A stable weight depends on a balance between the energy you get from food and the energy you use. You use energy during the day in three ways:
Basal metabolism accounts for about two-thirds of spent energy. Your body generally uses this energy to keep your temperature steady and the muscles of your heart and intestines working. Thermogenesis accounts for about 10% of spent energy.
When a person consumes more calories than the energy they use, the body stores the extra calories in fat cells (adipocytes). Fat cells function as energy reservoirs. They grow or shrink depending on how people use energy. If people do not balance energy input and output by eating right and exercising, fat can build up. This leads to weight gain.
When energy input is equal to energy output, there is no expansion of fat cells (adipocytes) to accommodate excess. When you take in more calories than you use, the extra fat is stored in your adipocytes and you begin to accumulate fat.
Obesity is determined by measuring body fat, not just body weight. People who are very muscular with low body fat may not be obese, even if their weight is over the limit for their height. Others might be at a normal weight or even underweight, but still have excessive body fat. The following measurements and factors are used to determine whether a person is overweight to a degree that threatens their health:
A person's disease risk factors and BMI are important components in determining the health risks of their weight.
Body Mass Index (BMI)
The current standard measurement for obesity is body mass index (BMI). A BMI of 25 to 29.9 is in the overweight category. Obesity is a BMI of 30 and above. A BMI of 40 or more is considered morbidly obese and usually means men are at least 100 pounds (45 kilograms) over their ideal weight and women are at least 80 pounds (36 kilograms) over their ideal weight.
Obesity is then classified into three categories:
These criteria may be used to estimate the risk for complications of obesity, such as diabetes, heart disease, or certain cancers. They are also used to help decide when surgery may be most appropriate.
Calculating Body Mass Index
You can calculate your BMI by dividing your weight in kilograms by your squared height in meters. (BMI calculators are available online.)
For example, a woman who is 5'6" (1.68 m) and weighs 130 pounds (59 kilograms) has a healthy BMI of 21. A woman at the same height who weighs 190 pounds (86 kilograms) will have a BMI of 30.7, corresponding to class 1 obesity.
You can check your BMI with the Centers for Disease Control and Prevention website -- BMI calculator.
Waist measurement is another way to estimate how much body fat a person has. Extra weight around the midsection or stomach area increases the risk for type 2 diabetes, heart disease, and stroke.
Some studies suggest that:
Excess body fat around the abdomen (the apple shape or android fat distribution) is a more consistent predictor of heart problems and health risks than BMI.
The distribution of fat can be evaluated by dividing waist size by hip size. For example, a woman with a 30-inch (76 cm) waist and 40-inch (102 cm) hip circumference would have a ratio of 0.75; a woman with a 41-inch (104 cm) waist and 39-inch (100 cm) hips would have a ratio of 1.05. The lower the waist-hip ratio, the better. The risk of heart disease rises sharply for women with ratios above 0.85 and for men with ratios above 1.0.
Anthropometry is the measurement of skin fold thickness in different areas, particularly around the triceps, shoulder blades, and hips. This measurement is useful for determining how much weight is due to muscle or fat.
Dual-energy x-ray absorptiometry
DXA is the most convenient and accurate method to measure the body composition. DXA takes only 10 to 20 minutes to scan whole body with very low radiation exposure.
Measuring body fat and diagnosing obesity is different in children and adults. In children, the amount of body fat changes with age. Because of this, BMI is harder to interpret during puberty and periods of rapid growth. In addition, girls and boys normally have different amounts of body fat.
A BMI that indicates obesity at one age may be normal for a child of a different age. To determine if a child is overweight or obese, experts compare BMI levels of children of the same age. They use a special chart to decide whether a child's weight is healthy or not.
Many people with obesity who lose large amounts of weight and gain it back often think it is their fault. They may blame themselves for not having the willpower to keep the weight off, and many regain more than they lost.
Today, we know that biology is part of the reason some people cannot keep weight off. Even among people who live in the same environment and eat the same foods, some become obese and others do not. Our bodies have a complex system to help keep weight at a healthy level. In some people, this system may not work correctly.
Think about the gas gauge in your car. If the gas tank is full but the car's gas gauge is broken, it may read empty. You would want to put in more gas, even when the tank is already full.
Some people struggle to maintain a healthy weight because one or more of the signals that tells the brain when they have eaten enough does not work correctly. In other words, the gas tank (stomach) may be full, but the brain (gas gauge) does not realize that.
Appetite is determined by processes that occur both in the brain and gastrointestinal tract. Eating patterns are controlled by areas in the hypothalamus (in the brain).
The body produces a number of molecules that increase or decrease appetite.
Leptin is a hormone that decreases appetite by reducing neuropeptide Y (NPY, a hunger stimulant) and by increasing a-melanocyte-stimulating hormone (a-MSH, a food intake inhibitor). A short-term increase in leptin levels decreases appetite, whereas falling levels of leptin induce hunger. Leptin is produced by fat cells and its blood levels rise as obesity develops. But appetite is not suppressed in obese people, although their leptin levels are increased, probably due to leptin resistance.
Ghrelin is another hormone that controls appetite. Ghrelin is mostly secreted by stomach cells and it works by telling the brain when the stomach is empty, causing hunger pangs and a decrease in metabolism (gastric bypass surgery reduces the size of the stomach and decreases levels of ghrelin).
Other hormones involved in the feeling of satiety are cholecystokinin (CCK), glucagon-like peptide 1 (GLP-1), apolipoprotein A-IV, and polypeptide YY.
Our bodies are set to maintain weight within a certain range. That weight range is at least partly determined by our genetic makeup. Genetic makeup refers to certain traits that we inherit from our parents. If a person has the genetic makeup for obesity and they eat a lot of high-calorie foods and do not exercise, it is almost certain they will become obese. It will likely be harder for such a person to stay at a healthy weight than someone who does not have the genes for obesity.
Obesity is not caused by just one gene. There are hundreds of genes that influence body weight. Some people have more genetic risk factors for obesity than others. However, scientists have not yet discovered the exact genes that contribute to obesity.
The way we eat when we are children may strongly affect our eating behaviors as adults. When we repeat these behaviors over many years, they become habits. They affect what we eat, when we eat, and how much we eat.
Children are very good at listening to their body's hunger and fullness signals. They will stop eating as soon as their body tells them they have had enough. However, at some point a well-meaning parent may tell them they have to finish everything on their plate. This forces them to ignore their fullness and to eat everything that is served to them.
As adults, these same people may say they feel guilty if they do not eat everything on their plate. And today, portion sizes are so large that eating everything on your plate may mean you are eating too many calories.
Other learned behaviors include using food to:
These learned habits lead to eating when someone is already full. Many people have a very hard time breaking these habits.
The foods we eat when we are children may influence our food likes and dislikes for life. Being raised on processed foods that are high in fat, salt, and sugar may make it difficult to start eating natural foods, such as fruits, vegetables, and whole grains, when we become adults. Not knowing how to prepare these foods can also keep people from eating them.
We are surrounded by many things that make it easy to overeat and hard to stay active.
Many people don't feel like they have enough time to plan and prepare healthy meals. This may be because they:
Less free time also means less time to exercise. Also, more people today work desk jobs, compared to more active jobs in the past.
Devices such as remote controls, mobile telephones, escalators, elevators, and computers all make life easier for us. But fewer trips up and down stairs and fewer walks down the hall at work to talk with a co-worker mean that we are storing more calories instead of burning them off.
Researchers have found that labor-saving devices have reduced people's energy usage by over 100 calories a day. The average American now eats 100 to 200 more calories a day than they did 10 years ago. Less activity and more calories can lead to a weight gain of 12 to 25 pounds (5 to 11 kilograms) every year.
Long hours in front of a TV or computer may be the most hazardous pattern of behavior. TV watching produces a lower metabolic rate than sewing, playing board games, reading, writing, and driving a car. And many people engage in unhealthy snacking and eating patterns while watching TV.
Many things have changed how and what we eat. Some of these are:
People are not only eating more food than they did 20 years ago, but they are also replacing home cooking with packaged foods, fast food, and dining out. Fast foods tend to be served in larger portions. They generally contain more calories and unhealthy fats, and fewer nutritious ingredients, than homemade or restaurant meals. Snack foods and sweet beverages, including juice and soft drinks, add to the increasing rates of obesity.
Several medical conditions may contribute to being overweight, but rarely are they a primary cause of obesity.
Some prescription medications contribute to weight gain, usually by increasing appetite. Such drugs include:
DO NOT stop taking any medications without first talking to your health care provider.
Where you live plays a role in your risk for obesity. For example, simply living in the United States makes a person more susceptible to obesity. The prevalence of obesity in America has risen dramatically over the past few years and continues to increase.
Fat tends to settle in certain regions, depending on gender. Women gain fat predominantly in the stomach, hips, and thighs, while men tend to gain fat in the belly and waist.
Risk by Age
People of any age are at risk for obesity. More children and adolescents are overweight in America than ever before. Gaining some weight is common with age, and adding about 10 pounds (5 kilograms) to a normal base weight over time is not harmful. The typical weight gain in American adults over 50, however, is worrisome. By age 55, the average American has added nearly 40 pounds (18 kilograms) of fat during the course of adulthood. This condition is made worse by the fact that muscle and bone mass decrease with age.
Risk by Gender
In men, BMI tends to increase until age 50 and then it levels off. In women, weight tends to increase until age 70 before it plateaus. There are 3 high-risk periods for weight gain in women:
Risk by Economic Group
Obesity is more prevalent in lower economic groups. Low-income people tend to have fewer fruits and vegetables and take in more calories a day than higher-income people. However, obesity is increasing in college-educated young adults, as well as in other groups. Fast food may also be cheaper and more accessible for many, while fresh produce and healthy foods are often more expensive and harder to find.
Among ethnic groups in general, African-American women are more overweight than Caucasian women, but African-American men are less obese than Caucasian men. Hispanic men and women tend to weigh more than Caucasians.
In many cases, lifestyle habits and patterns are so well-established and automatic that people are not even aware they are bad for health.
A number of dietary habits put people at risk for becoming overweight:
Anyone with a Sedentary Lifestyle
Office workers, drivers, and people who sit for long periods are at higher risk for obesity.
Nicotine increases the metabolic rate, and quitting, even without eating more, can cause weight gain. Most people who quit smoking gain 4 to 10 pounds (2 to 5 kilograms) in the first 6 months after quitting. Some gain as much as 25 to 30 pounds (11 to 14 kilograms). It is important to note that weight control is not a valid reason to smoke.
People with Disabilities
Obesity rates are higher than average in people with physical or mental disabilities. Those with disabilities in the lower part of the body, such as the legs, are at highest risk.
People with Chronic Mental illnesses
People who have a chronic mental illness are at high risk for obesity and diabetes, most likely due to their lifestyle. In addition, many of the medications used to treat chronic mental illnesses can cause weight gain and increase the risk of diabetes.
Obesity has become a serious health problem in children and teenagers. A child who is overweight or obese is more likely to be overweight or obese as an adult.
Obese children are now developing health problems that used to be seen only in adults. When these problems begin in childhood, they often become more severe when the child becomes an adult.
Today 18% of children (ages 6 to 11) and 21% of adolescents (ages 12 to 19) are obese. The number of obese children and adolescents has more than tripled since the 1980s.
Children and adolescents
No single factor or behavior causes obesity. Obesity is caused by the many factors described above, including a person's habits, lifestyle, and environment. Genetics and some medical conditions also increase a person's chances of becoming obese.
Children are surrounded by many things that make it easy for them to overeat and harder to be active:
Biological Effect of Childhood Obesity on Adult Weight
Achieving a healthy weight becomes more difficult as children get older. The odds of obesity persisting into adulthood range from 20% in 4 years olds to 80% in teenagers. One reason for the persistence is biological. The fat cells change in number or mass depending on a person's age:
Obesity is a medical condition in which a high amount of body fat makes it hard for a person's internal organs to work well. This can cause poor health. People with obesity are at risk for developing a number of health problems.
Three things can be used to determine if a person's body fat puts them at risk for developing obesity-related diseases:
The higher the BMI, the greater the risk for certain diseases, such as heart disease, stroke, high blood pressure, type 2 diabetes, sleep apnea (pauses in breathing during sleep), and arthritis.
The risk of heart disease, hypertension, stroke, gout, and type 2 diabetes, rises sharply for women with waist-hip ratios above 0.85 and for men with ratios above 1.0.
Weight gain in the area around the waist (apple type) is more dangerous than weight gained around the hips and flank area (pear type). Fat cells around the gut and abdominal organs (visceral fat) have different qualities than those found in the hips and thighs (subcutaneous fat).
Apple shape obesity is more commonly associated with insulin resistance and diabetes, high blood pressure, and unhealthy cholesterol and lipid levels.
General Adverse Effects of Being Overweight (Not Obese)
It is still not clear if being overweight (a BMI of 25 to 29.9) harms healthy people with no risk factors for serious illnesses.
The risk for developing diabetes, gallstones, hypertension, heart disease, stroke, and various cancers rises according to how much an individual is overweight. Adults who are overweight in middle age face a poor quality of life as they age, with the quality declining the more they weigh.
Some argue that unhealthy diet and sedentary lifestyle cause the harm -- not the extra weight itself -- in people who are not severely obese.
Being slightly overweight (versus underweight) may be linked with a lower risk of mortality in the elderly.
People who are obese have almost three times the risk for heart disease as people of normal weight. Being physically unfit adds to the risk.
Obesity poses many dangers to the heart and circulatory system:
Obesity frequently associates with diabetes, high blood pressure, and sleep apnea, which all also increase the risk for stroke.
Type 2 Diabetes and Insulin Resistance
Most people with type 2 diabetes are overweight or obese, and weight loss may be the key to controlling the current epidemic of type 2 diabetes. The common factor appears to be insulin resistance -- that is, the body can no longer respond properly to insulin. This has the effect of increasing sugar levels in the blood, the hallmark of diabetes.
Insulin resistance is also associated with high blood pressure and abnormalities in blood clotting. Some research indicates that obesity is the one common element linking insulin resistance, type 2 diabetes, and high blood pressure.
Metabolic syndrome (also called syndrome X) is a cluster of conditions that is significantly associated with heart disease and higher mortality rates from all causes. The syndrome consists of obesity marked by abdominal fat, unhealthy cholesterol levels, high blood pressure, and insulin resistance.
The American Cancer Society's (ACS) cancer prevention guidelines stress the importance of keeping a healthy weight throughout life. The ACS indicates that healthy weight is even more important than eating specific healthy foods when it comes to cancer prevention.
Obesity has been associated with a higher risk for cancer in general, and specific cancers in particular. Studies have also suggested that restricting calories reduces the risk for cancer.
One way in which obesity may increase the risk for cancer is its association with high levels of hormones called growth factors, which can trigger rapid cell production, leading to cancer.
Obesity increases the risk of these cancers:
More weight puts pressure on the bones and joints. This can lead to osteoarthritis, a disease that causes joint pain and stiffness. People who are obese are also at higher risk for carpal tunnel syndrome and other problems involving nerves in their wrists and hands. Overweight individuals with knee osteoarthritis benefit from diet and exercise programs for weight loss, which can lead to less knee pain, and improved function and quality of life.
Abnormal amounts of body fat, either 10% to 15% too high or too low, can contribute to infertility in women. Obesity is especially related to certain infertility problems, such as uterine fibroids and menstrual irregularities. In men, obesity can contribute to reduced testosterone levels and erectile dysfunction.
Effect on Pregnancy
Obesity has many dangerous effects on pregnancy. These include a greater risk of developing high blood pressure, gestational diabetes (diabetes, usually temporary, that occurs during pregnancy), urinary tract infections, blood clots, prolonged labor, and higher fetal death rate in late stages of pregnancy. Obesity is also associated with increased rates of cesarean delivery. Infants of women who are obese are also at higher risk for neural tube birth defects, which affect the brain or spine, as well as other birth defects. Folic acid supplements, which are normally effective in preventing these conditions, may not be as protective in overweight women. Some evidence also suggests an association between obesity and stillbirths.
Obesity, especially moderate or severe obesity, also puts people at risk for hypoxia, a condition in which there is not enough oxygen to meet the body's needs. Obese people need to work harder to breathe. Their breathing muscles and lungs often do not work as well as those in thinner people.
Pickwickian syndrome, named for an overweight character in a Dickens novel, occurs in severe obesity when a lack of oxygen produces intense and chronic sleepiness and, eventually, heart failure.
Nonalcoholic Fatty Liver Disease
People with obesity, particularly if they also have type 2 diabetes, are at higher risk for a condition called nonalcoholic fatty liver disease (NAFLD), also called nonalcoholic steatohepatitis (NASH). This condition can cause liver damage that is similar to liver injury seen in alcoholism. NAFLD occurs in about 80% of people with type 2 diabetes, and 90% of people with high risk obesity. NASH can also occur in overweight children.
The incidence of gallstones is significantly higher in people with obesity. The risk for stone formation is also high if a person loses weight too quickly. In people on ultra-low-calorie diets, taking ursodeoxycholic acid (Actigall) may prevent gallstones.
People who are obese and who nap tend to fall asleep faster and sleep longer during the day. At night, however, it takes them longer to fall asleep, and they sleep less than people of normal weight. Studies have suggested that obesity not only interferes with sleep, but that sleep problems may actually contribute to obesity.
Obesity, particularly the apple shape, is strongly associated with sleep apnea, which occurs when the upper throat relaxes and closes from time to time during sleep. This closure temporarily blocks the passage of air. Sleep apnea is increasingly being viewed as a potentially serious health problem, which may lead to complications such as heart disease and stroke. Weight loss is often recommended to treat sleep apnea. Bariatric surgery is no better than conventional weight loss programs in managing obstructive sleep apnea.
Obstructive sleep apnea may also increase obesity. Some studies indicate that treating sleep apnea may help people lose abdominal fat.
Several studies have reported an association between depression and obesity, particularly in obese women. There may be a number of factors to explain the link. In some cases of atypical depression, people overeat and may gain weight. Overweight people may also become depressed because of social problems and a poor self-image.
There does not appear to be any association between depression and obesity in men.
One long-term study reported that overweight young women completed fewer years of school, were 20% less likely to be married, and had 10% higher rates of household poverty than their thinner peers. Obese young men were also less likely to be married, and their incomes were lower than their thinner peers. Nevertheless, studies consistently show that overweight males (both boys and men) are not as severely emotionally affected as females of any age. Women and girls tend to blame themselves for being heavy, while males tend to blame being overweight on outside factors.
Children and adolescents who are overweight have poorer health than other children. Studies are reporting unhealthy cholesterol levels and high blood pressure in overweight children and adolescents. Of great concern is the dramatic increase in type 2 diabetes in young people, which is largely due to the increase in overweight children.
Weight gain in children is also linked to asthma, gallbladder problems, sleep apnea, and liver abnormalities. Overweight girls seem more likely to enter puberty early, and subsequently to be at higher risk for breast cancer. It is not yet clear how many of these childhood problems persist in people who achieve normal weight as adults. Staying overweight into adulthood carries health risks.
For most people, changing behavior takes time. All the stages of change are important. A person can learn from each stage. One can go from "not thinking about it" to "thinking about the pros and cons" to "making small changes and figuring out how to deal with the hard parts" to "doing it" to "making it part of your life." Many people fall off track and go through the stages of change several times before change really lasts.
Lifestyle changes usually involve slip-ups. People should not give up because they slip from time to time. Instead, they should forgive mistakes and get back to work toward the goal of lifelong health.
A food journal is a good way to become aware of eating habits.
Think about what triggers, or prompts some of your eating habits. Is there something in your environment, such as a vending machine down the hall, that makes you eat when you are not hungry or choose an unhealthy snack? Does the way you feel make you want to eat?
Look at your journal and circle the common triggers. Some of them might be:
Start by focusing on the one or two triggers that occurred the most often during your week. Is there something you could do to avoid these triggers?
Some ways to avoid triggers are:
Some other ideas for replacing unhealthy habits with healthy ones are:
It may take a while to turn unhealthy habits into new, healthy ones. Since it took a while to form the old habits, it may take just as long to change them. Do not give up.
Childhood obesity is best treated by a non-drug, multidisciplinary approach, including diet, behavior modification, and exercise. Children should be screened for obesity at age 6, and referred to weight management programs if needed at that time. Moderate-to-intense programs have the highest rate of success with children and adolescents. These programs include counseling and behavior modifications.
Most children spend about 3 hours a day watching TV. When you add in other screen time activities, they spend closer to 5 to 7 hours a day. Current screen time guidelines recommend that children under age 2 have no screen time. Above age 2, children should limit screen time to 1 to 2 hours a day.
Children should have many chances to run, bike, and play sports during the day. CDC recommends that children age 2 and older get 60 minutes of activity every day. The activities should comprise of moderate to vigorous aerobic exercises. Some examples are:
Younger children have shorter attention spans than older children. They may be active for only 10 to 15 minutes at a time. The goal is still a total of 60 minutes of activity every day. These ideas may help non-athletic children become active:
Choosing healthy snacks and drinks for your children can be a challenge. There are many to choose from.
The best thing parents can do to motivate their kids to lose weight is to lose weight themselves, if they need to. Parents should lead the way and follow the advice they give their children.
Eating as a family is important. Have meals where everyone sits down and talks about their day. These meals should have some set rules, such as no lectures or teasing allowed. Family meals should be a positive experience. Meals should be cooked at home, and children should be involved in the meal planning. If they are old enough, they can help prepare meals.
Teaching parents healthy lifestyle skills may lead to a sustained weight reduction in moderately-obese children. More research is needed, however, to assess the benefits of home-based programs for the prevention of childhood obesity.
Commercial and Nonprofit Support Programs for Weight Loss
There are many different types of weight-loss programs. (This report cannot address all of the many commercial and nonprofit weight-loss programs currently available, nor can it assess their claims.)
Taking off Pounds Sensibly (TOPS), a nonprofit support organization with many local chapters, is one of the least expensive programs in the United States.
Most commercial programs, such as Weight Watchers, Jenny Craig, and NutriSystem, offer individual or group support, lifestyle changes, and packaged meals. These programs tend to be more expensive. There are few well-conducted studies on these programs.
Approach short-term goals regarding exercise and eating as something to learn, rather than perform. Also, plan ahead when eating out or at someone else's home.
Cognitive Behavioral Approaches
Most support programs use some form of cognitive behavioral methods to change the daily patterns associated with eating. They are very useful for preventing relapse after initial weight loss.
In these programs, you review a personal diary with a therapist or group to set realistic goals and identify patterns you can change. For instance, if you normally eat food while watching television, you may need to eat in another room instead.
Stress reduction and relaxation techniques may be helpful for some people with obesity, such as those whose weight is related to night-eating syndrome.
The weight-loss formula: calories used (including exercise) > calories eaten = weight loss.
This means that to lose weight, the number of calories you burn needs to be greater than the number of calories you get from foods and drinks. Even if you work out a lot, you will gain weight if you take in more calories than you burn.
For example, a 30- to 50-year-old woman who does not exercise needs about 1,800 calories a day to maintain her normal weight. A 30- to 50-year-old man who does not exercise needs about 2,200 calories to maintain his normal weight. For every hour of exercise they do, they will burn approximately:
Even without dieting, people will lose weight if they add any of these activities to their lifestyle. Doing strength-training can help to build/maintain lean body mass, which can help to increase the amount of calories your body uses throughout the day.
Many people sit all day at their jobs. They can add activity to their schedule before work, during work, at lunch, and after work.
People who exercise are more apt to stay on a diet plan. Exercise improves psychological well-being and replaces sedentary habits that usually lead to snacking. Exercise may even act as a mild appetite suppressant. Moreover, exercise improves overall health, even with only modest weight loss.
Be aware, however, that the pounds won't magically melt off. If a person exercises but doesn't diet, any actual pounds lost may be minimal due to simultaneous gain of muscle mass. But regardless of weight loss, a fit body will be healthier and will look more toned. In addition, exercise benefits the heart and vascular system and raises HDL (good) cholesterol levels, even with no weight loss.
The following are some suggestions and observations on exercise and weight loss:
Because obesity is one of the risk factors for heart disease and diabetes, anyone who is overweight should discuss their exercise program with a doctor before starting.
About 50 to 70 million Americans go on diets each year. No one diet is right for everyone. What works for one person may not work for another.
Before beginning a diet, look at your own eating and activity patterns. Then set goals for changing some of these patterns or behaviors. Set goals that are realistic for you; goals that you can reach and maintain.
A good diet is one you can follow for years. It is better to make moderate lifestyle changes than attempt severe short-term changes. It should keep your weight at a good level for you and keep you in good health. Some key features of any good weight-loss program or diet are:
Be cautious about any diet that:
Calorie restriction has been the cornerstone of obesity treatment. The standard dietary recommendations for losing weight are:
As a rough rule of thumb, one pound (450 grams) of pure body fat is the result of eating about 3,500 calories. A person could lose a pound a week by reducing daily caloric intake by about 500 calories a day.
The calorie requirements for sustaining basal metabolism can be accurately determined by indirect calorimetry. It can also be estimated using formulas such as the Mifflin St Jeor equation, considered the most accurate in estimating calorie needs for obese people. Calorie requirements for maintenance of weight or for weight loss depend on current weight, gender, age, and activity levels.
Fat intake should be no more than 30% of total calories. Most fats should be in the form of monounsaturated and polyunsaturated fats (such as olive oil or fish oil). Avoid saturated fats (found in animal products such as lard or butter).
Extreme diets of fewer than 1,100 calories per day carry health risks and are not recommended. Most of the initial weight loss is in fluids. Later, fat is lost, but so is muscle, which can account for more than 30% of the weight loss. No one should be on a very strict diet for longer than 16 weeks, or fast for weight loss.
There are a number of problems associated with extreme diets:
Pregnant women who excessively diet during the first trimester put their unborn children at risk for birth defects. Not gaining appropriate weight during pregnancy puts the fetus at risk for life-long health issues.
Eating a balanced diet means you consume the right types and amounts of foods and drinks to keep your body healthy.
For protein in the diet, choose:
Consume 3 cups per day of fat-free or low-fat milk or milk products. Items such as cream cheese, cream, or butter do not count as healthy dairy products.
Grain products include any food made from wheat, rice, oats, cornmeal, barley, or another cereal grain. Products made with grains can include pasta, oatmeal, breads, breakfast cereals, tortillas, and grits.
Grains are divided into either whole grains or refined grains. The key to eating healthy is to choose mostly whole-grain products.
Oils are fats that are liquid at room temperature. Most oils are high in monounsaturated or polyunsaturated fats. This is the best type of oil to use in cooking or preparing foods. Solid fats are solid at room temperature. All of these contain saturated fats. Saturated fats are much less healthy for your heart, blood vessels, and other parts of your body.
Eat 2 cups (4 servings) of fruit and 2 1/2 cups of vegetables (5 servings) per day for an average 2,000-calorie daily diet.
Low carbohydrate diets generally restrict the amount of carbohydrates but do not restrict protein sources.
The Atkins diet restricts complex carbohydrates in vegetables and, particularly, fruits that are known to protect against heart disease. The Atkins diet can cause excessive calcium excretion in the urine, which increases the risk for kidney stones and osteoporosis. This is a weight loss diet and not designed for long term health.
Low-carb diets, such as South Beach, The Zone, and Sugar Busters, rely on a concept called the glycemic index, or GI, which ranks foods by how high and how quickly they cause blood sugar levels to rise. Foods on the lowest end of the index take longer to digest. Slow digestion wards off hunger pains. It also helps stabilize insulin levels. Foods high on the glycemic index include bread, white potatoes, and pasta, while low-glycemic foods include whole grains, fruit, lentils, and soybeans.
There has been debate about whether Atkins and other low-carbohydrate diets can increase the risk for heart disease, because people who follow these diets tend to eat more saturated fat and animal protein and less fruits and vegetables. In general, these diets appear to lower triglyceride levels and raise HDL (good) cholesterol levels. Total cholesterol and LDL (bad) cholesterol levels tend to remain stable or possibly increase somewhat. However, large studies have not found an increased risk for heart disease, at least in the short term. In fact, some studies indicate that these diets may help lower blood pressure -- another heart disease risk.
Low-carbohydrate diets help with weight loss in the short term, possibly even better than low-fat, normal carbohydrate diets. However, overall, there isn't good evidence showing the long-term effectiveness of low-carbohydrate diets. Their long-term safety and other possible health effects are still a concern, especially since these diets restrict healthy foods, such as fruit, vegetables, and grains, and they don't restrict saturated fats.
Replacing fats and sugars with substitutes may help many people who have trouble maintaining their weight.
Fat substitutes added to commercial foods or used in baking deliver some of the desirable qualities of fat, without adding as many calories. They cannot be eaten in unlimited amounts, however, and are considered most useful for helping keep down total calorie count.
Olestra (Olean) passes through the body without leaving behind any calories from fat. Studies suggest that it helps improve cholesterol levels and may help overweight people lose weight. Early reports of cramps and diarrhea after eating food containing olestra have not proven to be significant. Of greater concern is the fact that even small amounts of olestra deplete the body of certain vitamins and nutrients that may help protect against serious diseases, including cancer. The FDA requires that the missing vitamins, but not other nutrients, be added back to olestra products.
Beta-glucan is a soluble fiber found in oats and barley. Products using this substance (Nu-Trim) may reduce cholesterol and have additional health benefits.
A number of other fat-replacers are also available. Although studies to date have not shown any significant adverse health effects from these products, their effect on weight control is uncertain, since many of them may be high in sugar. People who learn to cook using foods that are naturally lacking or low in fat will eventually lose their taste for high-fat foods, but the same may not be true for people who use fat substitutes.
Many artificial or low-calorie sweeteners are available. Yet using these artificial sweeteners should not give dieters a license to increase their fat intake. There has been some concern about the chemicals used to produce many of these sweeteners. Natural low-calorie sweeteners may be more acceptable to many people.
Other sugar substitutes being investigated include glycyrrhizin (derived from licorice) and dihydrochalcone (derived from citrus fruits).
Some studies have reported good success with meal replacement beverages (such as Slim-Fast and Sweet Success). They contain major nutrients needed for daily requirements. Each serving typically contains 200 to 250 calories and replaces one meal. (Note: Using these replacement products for all meals severely reduces calories and can be harmful.)
Weight loss programs can cost about $2,000. People who complete these programs may lose close to 10% of their weight. For example, someone who started at 200 pounds (90 kilograms) may loses 20 pounds (9 kilograms), on average. But many people regain over half of the lost weight over time.
There are several different drugs used for weight loss. Unless specifically instructed by a doctor, people should use non-drug methods for losing weight. Except under rare circumstances, pregnant or nursing women should never take diet medications of any kind, including herbal and over-the-counter remedies. While weight loss drugs in general have shown some benefit, the overall weight loss achieved is generally limited, generally around a 5% weight loss. In addition, people will usually regain the weight when they stop the medication.
Weight loss medications improve several risk factors for heart disease. However, use of obesity medication has not yet been shown to lower the risk for heart disease, stroke, and related problems. More research is necessary.
About 7% of American adults use nonprescription weight-loss products. People must be cautious when using any weight-loss medications, including over-the-counter diet pills and herbal remedies. Buying unverified products over the Internet can be particularly dangerous.
Some studies have suggested that regular tea drinking is associated with lower weight, particularly in people who drink it for years. However, better evidence is needed to confirm the results.
Thermogenic Approach to Weight Loss
An approach to weight loss called thermogenic (or hepatothermic) therapy is based on the claim that certain natural compounds have properties that enable the liver to increase energy in cells and stimulate metabolism. Theoretically, the result would be fat loss. Among the substances used in such products are EPA-rich fish oil, sesamin, hydroxycitrate, pantethine, L-carnitine, pyruvate, aloe vera, aspartate, chromium, coenzyme Q10, green tea polyphenols, DHEA derivatives, cilostazol, diazoxide, and fibrate drugs.
Nearly all the current over-the-counter dietary aids contain some combination of these ingredients. There is no evidence that any of these ingredients can produce weight loss, and some may even have harmful effects.
Chromium is a common ingredient in many diet supplements (such as Xenadrine, Dexatrim, Acutrim Natural, and Twinlab Diet Fuel). It is claimed to specifically promote fat loss, rather than lean muscle loss. There is no proof that chromium helps with weight loss.
Ephedra, Ephedrine, and Ma Huang
The FDA does not allow the sale of drugs that contain ephedrine. In May 2004, the FDA banned the sale of dietary supplements that contain ephedra (also called Ma Huang). Ephedra can cause serious side effects, including strokes and heart attacks.
Brazilian Diet Pill
The FDA has warned consumers not to buy a product known as the Brazilian diet pill. This product is labeled as a dietary supplement, but it contains several chemicals found in powerful prescription drugs.
Conjugated Linoleic Acid (CLA)
Conjugated linoleic acid is found in many dietary products. There is no evidence that it produces weight loss. Furthermore, there is some concern that CLA might increase insulin resistance and a dangerous inflammatory response in people with obesity.
Over-the-counter products containing tiratricol, a thyroid hormone analogue, have been sold for weight loss. Such products may increase the risk for thyroid disorders, heart attack, and stroke. Tiratricol is also known as triiodothyroacetic acid or TRIAC.
Laxative Actions in Natural Substances
Many dietary herbal teas contain laxatives, which can cause gastrointestinal distress. If overused, they may lead to chronic pain, constipation, and dependency. Rarely, dehydration and death have occurred. Some laxative substances found in teas include senna, aloe, buckthorn, rhubarb root, cascara, and castor oil.
Some fiber supplements containing guar gum have caused obstruction of the esophagus and gastrointestinal (digestive) tract.
Chitosan, a dietary fiber from shellfish, prevents a small amount of fat from being absorbed in the intestine. Well-conducted studies have not found it to be effective. People who are allergic to shellfish should not take these supplements.
Dietary remedies that list the ingredient plantain may contain digitalis, a powerful chemical that affects the heart. NOTE: This substance should not be confused with the harmless banana-like plant also called plantain.
Orlistat (Xenical) can help about one-third of obese patients lose a modest amount of weight, and can help in long-term maintenance of weight loss. Most often, it is recommended as the first line drug therapy for obesity. It works by inhibiting enzymes that digest fats and slowing the absorption of fat in the intestine by about 30%. The average weight loss attained with this drug is around 6 pounds (~3 kilograms). However, many people regain a significant portion of this weight within 2 years. While orlistat does not work for all patients, it can improve cholesterol levels, regardless of weight loss, as well as lower blood pressure.
Orlistat can cause gastrointestinal problems and may interfere with the absorption of the fat-soluble vitamins A, D, and E and other important nutrients. The FDA recommends taking a daily multivitamin supplement when using this drug.
The most unpleasant side effect is leakage of oily feces from the anus. Restricting fats can reduce this effect. People with bowel disease should probably avoid orlistat. Despite these side effects, most patients are able to tolerate this medicine. Severe liver disease and kidney injury has rarely been reported with orlistat.
There is an approved over-the-counter version of orlistat. Sold under the name Alli, it is available at half the prescription strength of Xenical. Those eager to use it should consider its cost and modest benefits compared with its side effects.
The FDA approved Qsymia (phentermine and topiramate), Contrave (bupropion and naltrexone) and Belviq (lorcaserin Belviq) for use in obese adults with a BMI greater than 30, or for adults with a BMI greater than 27 who also have a weight-related medical problem, such as type 2 diabetes, hypertension, or dyslipidemia. These drugs are to be used in conjunction with lifestyle measures of dieting and physical activity. Doctors are looking for a weight loss of 3% to 5% or more in 12 weeks. If this weight loss does not occur, the medication should not be continued. Pregnant women and women who are planning to become pregnant should not take either of these drugs.
The only other long-term obesity medication approved by the FDA is Xenical (orlistat), described above.
Liraglutide (Saxenda) is approved as the fifth available obesity drug in the United States. It is approved for use in people with a BMI greater than 30 or when a medical problem such as high blood pressure, diabetes, or elevated cholesterol is present in people with a BMI greater than 27.
Phentermine and Other Sympathomimetics
Sympathomimetics are drugs that act like the stress hormone (and chemical messenger) norepinephrine. These medications act as stimulants in the brain. Some are approved for treating obesity, but only for short-term use of 12 weeks or less. Average weight loss has been in the range of 7 pounds (3 kilograms) over the short-term. These medicines include:
Phentermine is the most commonly prescribed appetite suppressant, and it is less expensive than orlistat or sibutramine. Phentermine combined with topirimate is discussed just above. Its effects are not long lasting, however. It can also raise blood pressure. In addition, phentermine is associated with depression, which is already a problem in many cases of obesity. Note: Neither phentermine nor its current combinations are associated with the heart problems linked to the previous phentermine combination known as Fen-Phen (phentermine and fenfluramine).
Bariatric surgeries produce weight loss through 2 mechanisms:
Gastric banding and sleeve gastrectomy are restrictive procedures.
Gastric bypass (also called Roux-en-Y gastric bypass) creates a smaller stomach, but also reroutes or bypasses a portion of the small intestine. As a result, greater weight loss is achieved than with procedures that only create a smaller stomach.
The surgeries above are almost always done through laparoscopic approaches. This involves 5 to 6 small cuts in the abdomen for instruments and for a camera that allows the surgeon visual access.
Biliopancreatic diversion with a duodenal switch (BPD surgery) is more complex than other weight-loss surgeries and is done much less often -- usually only for severe, morbid obesity. The surgeon removes a large portion of the stomach and re-routes the passage of food so it does not pass through most of the small intestine, where food is normally absorbed (it is restrictive and malabsorptive).
Bariatric surgery requires specialized expertise and facilities. Studies have shown that the likelihood of complications is significantly associated with the experience of the surgeon and staff. A team approach with attention to dietary and metabolic needs is vital.
Patients must still develop a healthy lifestyle and be calorie conscious after weight-loss surgery. Follow-up must be lifelong. Those who are able to change their lifestyle can expect to lose 30% to 50% of their excess weight, depending on the procedure.
Outcomes after gastric bypass surgery and sleeve gastrectomy are better than outcomes after gastric banding.
Bariatric surgery can reduce the risk of disease in people with severe obesity. These risks include diabetes, high blood pressure, heart disease, stroke, obstructive sleep apnea, arthritis, and some cancers. Successful weight loss after surgery can also lead to improvements in people who already have these conditions.
Losing weight should also make it much easier for the patient to move around and do everyday activities.
Weight-loss surgery alone is not a solution to losing weight. It can train you to eat less, but you still have to do much of the work. To lose weight and avoid complications from the procedure, you will need to follow exercise and eating guidelines from your doctor and dietitian.
Surgery may be used for individuals who have been severely obese for 5 years or more and have not responded to other weight-loss therapies, such as diet, exercise, or medications.
Body mass index (BMI) is the most common measure of obesity. BMI measures weight in relation to height.
Doctors often use the following BMI measures to identify patients who may be most likely to benefit from weight-loss surgery:
Some experts now support weight-loss surgery for most patients with a BMI of 30 or greater who have diabetes. Weight-loss surgery appears to produce better glucose control than medical therapy alone in patients with type 2 diabetes.
Your doctor must also consider medical problems that could make surgery more risky for you. These include:
Patients with binge eating disorder should be identified and treated before surgery. A full evaluation, including a psychological evaluation, should be performed on all candidates for surgery.
Patients who are considering bariatric surgery should be well-informed regarding the procedure, its effectiveness, side effects, and complications. They should also understand the following:
Is weight-loss surgery safe for teens?
In laparoscopic gastric banding, the surgeon places a band around the upper part of the stomach to create a small pouch to hold food. After surgery, the doctor can adjust the band to make food pass more slowly or quickly through your digestive system. The band around your stomach is filled with saline (saltwater). It is connected to a container (access port) that is placed under your skin in your upper belly. Your surgeon can make the band tighter or looser by increasing or decreasing the amount of saline in the band. To do this, your surgeon will insert a needle through your skin into the access port.
Most people go home the same day of surgery. Some will stay 1 night in the hospital. Most people take 1 week off of work.
The average weight loss is about one-third to one-half of your extra weight. This may be enough. The weight will usually come off more slowly than with gastric bypass. You should keep losing weight for up to 3 years.
The band is removable, if necessary. Studies to date indicate that the intestinal tract returns to normal afterward. Studies, including those done in the elderly, have reported significant weight loss and improved quality of life with the procedure.
In gastric bypass, the stomach is divided with staples into two parts. The first part is very small, about the size of a golf ball. This small stomach is called the pouch. The second part of the stomach is much bigger, but food cannot go into it.
The small intestine is connected to the small pouch, which re-routes food around the big part of the stomach. The pouch can only hold a small amount of food, so if you eat too much or too fast you will throw up. Also, your body will not absorb all the calories in the food you eat.
Most people stay in the hospital for 2 days after open surgery. You may have a drain (tube) coming out of the stomach, which will drain fluids that build up after surgery. The drain tube is usually taken out about 7 to 10 days after surgery.
You may need to take 3 to 4 weeks off from work. If the work does not involve too much physical activity, you may be able to return sooner.
Total weight loss in the short term after bypass surgery is usually greater than after gastric banding and somewhat better than sleeve gastrectomy.
In the gastric sleeve surgery, a large portion of the stomach is removed. The new, smaller stomach is about the size of a banana. It limits the amount of food you can eat by making you feel full after eating only small amounts. The procedure can be performed with tiny incisions in the abdomen and a camera for viewing. Operating time and complications may be lower with laparoscopic sleeve gastrectomy compared to bypass procedures.
Most people can go home 2 days after the surgery. You should be able to drink clear liquids on the day after surgery, and eat a puréed diet by the time you go home.
The final weight loss may be close but generally is not quite as large as with gastric bypass. However, it may be enough for many people. Long-term reporting of outcomes from well-designed studies is still considered lacking however. Consult with your doctor about which procedure is best for you.
Weight will usually come off more slowly after gastric sleeve surgery than after gastric bypass. People who have gastric sleeve surgery should keep losing weight for up to 2 to 3 years.
Risks common to all weight-loss surgeries are:
These problems with a gastric band or access port may occur:
These problems may occur after gastric bypass:
After vertical sleeve gastrectomy, stomach contents may leak from the area where the remaining parts of the stomach are stapled together. You may need another operation to repair this problem if it occurs.
Most people stay in the hospital for a few days after gastric bypass surgery. You will be discharged when you can:
You will continue to eat a liquid or soft diet for several weeks after the surgery. After a pouch procedure, the pouch eventually expands to hold about 1 cup (250 mL) of chewed food (a normal stomach can about 1 quart or 1 liter).
Follow-up appointments are essential to determine if you need nutritional supplements such as iron, calcium, or vitamin B12. Supplements, such as a multivitamin with minerals, may be prescribed.
Eat small meals (usually six) throughout the day, rather than large meals that the stomach can no longer handle.
The new stomach probably won't be able to handle both solid food and fluids at the same time. Separate fluid and food intake by at least 30 minutes and only sip what you are drinking.
After surgery, you will have less tolerance of fat, alcohol, and sugar. Reduce your fat intake, especially:
Exercise and the support of others (for example, joining a support group with people who have undergone weight-loss surgery) are extremely important to achieving and maintaining weight loss after bariatric surgery.
You can usually start exercising 6 weeks after the operation. Even sooner than that, you should be able to take short walks at a comfortable pace, after consulting with your doctor.
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Reviewed By: Steven Kang, MD, Director, Cardiac Electrophysiology, Alta Bates Summit Medical Center, Stanford Healthcare, Oakland, CA. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.