Definition & Facts

In this section:

• What are overweight and obesity?
• How common is overweight and obesity?
• Who is more likely to be overweight?
• Who is more likely to have obesity?
• Why do people gain weight?
• Who should lose weight?

What are overweight and obesity?

The terms “overweight” and “obesity” refer to body weight that is greater than what is considered normal or healthy for a certain height. Overweight is generally due to extra body fat. However, overweight may also be due to extra muscle, bone, or water. People who have obesity usually have too much body fat.

Your body mass index (BMI) is one way to tell if you are at a healthy weight, overweight, or have obesity. The BMI is a measure based on your weight in relation to your height. The greater your BMI, the greater your risk of health problems from overweight and obesity.

Reaching and staying at a healthy weight may be a long-term challenge if you are overweight or have obesity. Maintaining a healthy weight—or at least not gaining more weight if you are already overweight—can help lower your chance of developing certain health problems.

How common is overweight and obesity?

According to a national U.S. survey^1,2,3

• more than 1 in 3 adults were considered to be overweight
• more than 1 in 3 adults were considered to have obesity
• more than 2 in 3 adults were considered to be overweight or have obesity

For more statistics on overweight and obesity in the United States, see NIDDK’s Overweight & Obesity Statistics.

Who is more likely to be overweight?

Men are more likely than women to be overweight.³

Who is more likely to have obesity?

According to a national U.S. survey, some groups are more likely to have obesity.²

• Among black adults, 48 out of 100 were considered to have obesity.
• Among Hispanic adults, 42 out of 100 were considered to have obesity.
• Among white adults, 36 out of 100 were considered to have obesity.

Women are more likely than men to have obesity.²

Many factors play a role in who is more likely to have obesity, and these factors may affect people differently.

Why do people gain weight?

Many factors may cause weight gain and affect how much weight your body stores. When you take in more calories from food or beverages than you use up from physical activity and through daily living, such as sitting or sleeping, your body stores the extra calories. Over time, if you continue to consume more calories than you burn off, you will likely gain weight. Excessive weight gain may lead to overweight or obesity.

Who should lose weight?

Medical experts recommend that people who have obesity should lose weight.

Most people who are overweight and have one or more factors that raise their chance for heart disease should lose weight. These factors include

• diabetes
• prediabetes
• high blood pressure
• dyslipidemia—high levels of LDL cholesterol, low levels of HDL cholesterol, or high levels of triglycerides
• a large waist size—for men, greater than 40 inches; for women, greater than 35 inches

References

Factors Affecting Weight & Health

What factors affect weight and health?

Many factors can affect your weight and lead to overweight or obesity. Some of these factors may make it hard for you to lose weight or avoid regaining weight that you’ve lost.

Family history and genes

Overweight and obesity tend to run in families, suggesting that genes may play a role. Your chances of being overweight are greater if one or both of your parents are overweight or have obesity. Your genes may affect the amount of fat you store in your body and where on your body you carry the extra fat.

Race or ethnicity

Some racial and ethnic minority groups are more likely to have obesity. Obesity rates in American adults are highest in African Americans, followed by Hispanics/Latinos, then Caucasians. This is true for men and women.⁴ While Asian American men and women have the lowest rates of obesity,⁴ they can still be at risk of diseases associated with obesity if they carry a lot of unhealthy fat in their abdomen—even when their body mass index (BMI) is lower.⁵

Age

Many people gain weight as they age. Adults who have a normal BMI often start to gain weight in young adulthood and continue to gain weight until they are ages 60 to 65. In addition, children who have obesity are more likely to have obesity as adults.

Sex

In the United States, obesity is more common in black or Hispanic women than in black or Hispanic men.⁴ A person’s sex may also affect where the body stores fat. Women tend to build up fat in their hips and buttocks. Men usually build up fat in their abdomen or belly. Extra fat, particularly if it is around the abdomen, may put people at risk of health problems even if they have a normal weight.

Eating and physical activity habits

Your eating and physical activity habits may raise your chances of becoming overweight and having obesity if you

• eat and drink a lot of foods and beverages that are high in calories, sugar, and fat
• drink a lot of beverages that are high in added sugars
• spend a lot of time sitting or lying down and have limited physical activity

Where you live, work, play, and worship

Where you live, work, play, and worship may affect your eating and physical activity habits, and access to healthy foods and places to be active.

For example, living in an area that has a high number of grocery stores can increase your access to better quality, lower calorie foods. Living in a neighborhood with a lot of green spaces and areas for safe physical activity may encourage you to be more physically active.

Where you work and worship may also make it easier for you to eat unhealthy, high-calorie foods. Vending machines, cafeterias, or special events at your workplace or place of worship may not offer healthy, lower calorie options. Whenever possible, choose the healthier options and limit your treats to a small sliver of pie or cake.

Family habits and culture

Family eating and lifestyle habits may affect your weight and health. Some families may consume foods and beverages that are high in fat, salt, and added sugars or eat large amounts of unhealthy foods at family gatherings. Some families may also spend a lot of inactive time watching TV, using a computer, or using a mobile device instead of being active.

Your social, ethnic, or religious group culture may also affect your weight and health because of shared eating and lifestyle habits. Some cultures may consume foods and beverages that are high in fat, salt, and added sugars. Some common food preparation methods, such as frying, may lead to high-calorie intake. Regularly consuming foods high in calories, fat, and sugar may lead to weight gain overtime.

Not enough sleep

People who don’t get enough sleep may eat more calories and snack more.⁶ Experts recommend that adults ages 18 to 64 get 7 to 9 hours of sleep a day, and that adults ages 65 and older get 7 to 8 hours of sleep a day.⁷

Other factors

Other factors that can lead to weight gain include

• certain medical conditions
• certain medicines
• binge eating disorder
• stress

What makes it hard for some people to lose weight?

Many factors can make it hard to lose weight, including

• your genes
• what and how much you eat
• not getting regular physical activity or being inactive
• taking certain medicines
• having certain medical conditions
• Difficulty in managing stress

References

Am I at a Healthy Weight?

How can I tell if I am at a healthy weight?

Knowing your body mass index (BMI), waist size, and waist-to-hip ratio can help you tell if you’re at a healthy weight.

Body mass index

The BMI is the tool most commonly used to estimate and screen for overweight and obesity in adults. BMI is a measure based on your weight in relation to your height. You can easily calculate your BMI.

Your BMI can tell if you are at a normal or healthy weight, are overweight, or have obesity. The greater your BMI, the greater your risk of health problems such as type 2 diabetes and heart disease.

• Normal or healthy weight. A person with a BMI of 18.5 to 24.9 is in the normal or healthy range.
• Overweight. A person with a BMI of 25 to 29.9 is considered overweight.
• Obesity. A person with a BMI of 30 to 39.9 is considered to have obesity.
• Extreme obesity. A person with a BMI of 40 or greater is considered to have extreme obesity.

Because BMI doesn't measure actual body fat, a person who is very muscular, like a bodybuilder, may have a high BMI without having a lot of body fat. Also, some groups who tend to have a lower BMI, such as Asian men and women or older adults, may still have high amounts of body fat even if they are not overweight.

Waist size

Another important measure is your waist size. Having too much fat around your waist may raise your chances of health problems even more than having fat in other parts of your body. Women with a waist size of more than 35 inches and men with a waist size of more than 40 inches may be more likely to develop diseases related to obesity.

Does my body shape matter?

Doctors are concerned not only with how much body fat you have, but where the fat is located on your body. Women tend to build up fat in their hips and buttocks, giving them a “pear” shape. Men usually build up fat in their abdomen, giving them more of an “apple” shape. Of course, some men are pear-shaped, and some women are apple-shaped.

Extra fat, especially in the abdomen, may put people at risk for certain health problems, even if they have a normal weight. People who are apple-shaped may be more likely to develop type 2 diabetes, heart disease, or certain types of cancer than people of the same weight who are pear-shaped.

When should I seek a doctor’s help?

You should seek a doctor’s help if you are gaining weight quickly, have a large waist size, or a BMI of 30 or greater. You should also seek a doctor’s help if you are overweight or have obesity and have

• a family history of certain diseases, such as type 2 diabetes or heart disease
• health problems such as type 2 diabetes, heart disease, or metabolic syndrome

Health Risks

Overweight and obesity may raise your risk for certain health problems and may be linked to certain emotional and social problems.

What are some health risks of overweight and obesity?

Type 2 diabetes

Type 2 diabetes is a disease that occurs when your blood glucose, also called blood sugar, is too high. About 8 out of 10 people with type 2 diabetes are overweight or have obesity.⁸ Over time, high blood glucose leads to problems such as heart disease, stroke, kidney disease, eye problems, nerve damage, and other health problems.

If you are at risk for type 2 diabetes, losing 5 to 7 percent of your body weight and getting regular physical activity may prevent or delay the onset of type 2 diabetes.

High blood pressure

High blood pressure, also called hypertension, is a condition in which blood flows through your blood vessels with a force greater than normal. High blood pressure can strain your heart, damage blood vessels, and raise your risk of heart attack, stroke, kidney disease, and death.

Heart disease

Heart disease is a term used to describe several problems that may affect your heart. If you have heart disease, you may have a heart attack, heart failure, sudden cardiac death, angina, or an abnormal heart rhythm. High blood pressure, abnormal levels of blood fats, and high blood glucose levels may raise your risk for heart disease. Blood fats, also called blood lipids, include HDL cholesterol, LDL cholesterol, and triglycerides.

Losing 5 to 10 percent of your weight may lower your risk factors for developing heart disease. If you weigh 200 pounds, this means losing as little as 10 pounds. Weight loss may improve blood pressure, cholesterol levels, and blood flow.

Stroke

Stroke is a condition in which the blood supply to your brain is suddenly cut off, caused by a blockage or the bursting of a blood vessel in your brain or neck. A stroke can damage brain tissue and make you unable to speak or move parts of your body. High blood pressure is the leading cause of strokes.

Sleep apnea

Sleep apnea is a common disorder in which you do not breathe regularly while sleeping. You may stop breathing altogether for short periods of time. Untreated sleep apnea may raise your risk of other health problems, such as type 2 diabetes and heart disease.

Metabolic syndrome

Metabolic syndrome is a group of conditions that put you at risk for heart disease, diabetes, and stroke. These conditions are

• high blood pressure
• high blood glucose levels
• high triglyceride levels in your blood
• low levels of HDL cholesterol (the “good” cholesterol) in your blood
• too much fat around your waist

Fatty liver diseases

Fatty liver diseases are conditions in which fat builds up in your liver. Fatty liver diseases include nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH). Fatty liver diseases may lead to severe liver damage, cirrhosis, or even liver failure.

Osteoarthritis

Osteoarthritis is a common, long-lasting health problem that causes pain, swelling, and reduced motion in your joints. Being overweight or having obesity may raise your risk of getting osteoarthritis by putting extra pressure on your joints and cartilage.

Gallbladder diseases

Overweight and obesity may raise your risk of getting gallbladder diseases, such as gallstones and cholecystitis. Imbalances in substances that make up bile cause gallstones. Gallstones may form if bile contains too much cholesterol.

Some cancers

Cancer is a collection of related diseases. In all types of cancer, some of the body’s cells begin to divide without stopping and spread into surrounding tissues. Overweight and obesity may raise your risk of developing certain types of cancer.

Kidney disease

Kidney disease means that your kidneys are damaged and can’t filter blood like they should. Obesity raises the risk of diabetes and high blood pressure, the most common causes of kidney disease. Even if you don’t have diabetes or high blood pressure, obesity itself may promote kidney disease and quicken its progress.

Pregnancy problems

Overweight and obesity raise the risk of health problems that may occur during pregnancy. Pregnant women who are overweight or obese may have a greater chance of

• developing gestational diabetes
• having preeclampsia—high blood pressure during pregnancy, which can cause severe health problems for mother and baby if left untreated
• needing a cesarean section, or C-section and, as a result, taking longer to recover after giving birth

What emotional and social problems are linked to overweight and obesity?

Overweight and obesity are associated with mental health problems such as depression. People who deal with overweight and obesity may also be the subject of weight bias and stigma from others, including health care providers. This can lead to feelings of rejection, shame, or guilt—further worsening mental health problems.

References

Eating & Physical Activity

What options might help you lose weight?

Changing your eating habits is central to losing and maintaining your weight. To lose weight, you have to eat fewer calories and use more calories than you take in. This can be challenging for many people to do for an extended period of time. Emerging research shows that sticking with an eating plan may be more important to losing and maintaining weight than the type of eating plan you follow.

Follow a healthy eating plan

All your food and beverage choices count. Eating healthy is a journey shaped by many factors, including your age, weight, metabolism, food preferences, access to food, culture, and traditions; whether you are a man or woman; and the personal decisions you make over time. A healthy eating plan includes

• a variety of vegetables, fruits, and whole grains, such as brown rice, oats, and whole-wheat bread
• fat-free or low-fat dairy products such as milk, yogurt, and cheese and similar products such as soy beverages
• a variety of protein foods, including seafood, lean meats and poultry, eggs, legumes (beans and peas), nuts, seeds, and soy products
• oils, such as olive and canola oils and those found in nuts, olives, and avocados

A healthy eating plan also includes

• consuming fewer foods and beverages that have refined carbohydrates, added sugars, and salt (sodium)
• controlling portion sizes
• limiting foods with saturated fats and trans fats, like those found in desserts and fried foods

To learn more about a healthy eating plan and the amounts of food and beverages that are right for you, visit ChooseMyPlate.gov.

Get regular physical activity

The Physical Activity Guidelines for Americans, 2nd edition (PDF, 14.2 MB) define regular physical activity as at least 150 minutes a week of moderate-intensity aerobic activity, such as brisk walking. A moderate-intensity aerobic activity makes your heart beat faster and makes you breathe harder but does not overwork or overheat you. This type of physical activity is safe for most people.

People with physical disabilities also can do certain activities, such as wheelchair aerobics or basketball. Talk with your doctor about the types of physical activity that might work well with your abilities.

If you have a health condition such as heart disease, high blood pressure, or diabetes, talk with your doctor before you start regular physical activity. Your doctor can review with you the types and amounts of physical activity that might suit your lifestyle, interests, and skills.

Read Tips to Help You Get Active.

What should I do to stay at a healthy weight?

Recent research has found there are many reasons why it is difficult to keep weight off after losing weight. In addition to metabolism slowing during weight loss, your body needs fewer calories at your new, lower weight. Hormonal and other factors also tend to promote weight regain. People who have kept weight off long-term report needing to keep careful track of their food intake and to do high levels of physical activity. Some people who have reached a healthy weight may find it hard to keep the weight off.

Keep track of your weight

Weigh yourself regularly. Keep a record of your weight to help make sure you are maintaining your weight loss and not regaining weight.

Stick to your healthy eating plan

Continue to make healthy food choices, and make following your healthy eating plan a lifelong habit. Find healthy food options that you prefer and enjoy, as you are more likely to stick with your eating plan.

Continue regular physical activity

Regular physical activity may help you keep from regaining weight you’ve lost. Aim for at least 300 minutes a week of moderate-intensity physical activity to prevent regaining weight.⁹ Make regular physical activity a lifelong habit.

Take part in a weight-loss maintenance program

If you were overweight or had obesity and lost weight, your doctor may advise you to take part in a program to help you maintain your weight loss. The program may help you stick to your healthy eating and regular physical activity plan, and track your progress.

References

Treatment

In this section:

• Healthy eating plan and regular physical activity
• Changing your habits
• Weight-management programs
• Weight-loss medicines
• Weight-loss devices
• Bariatric surgery
• Special diets

Common treatments for overweight and obesity include losing weight through healthy eating, being more physically active, and making other changes to your usual habits. Weight-management programs may help some people lose weight or keep from regaining lost weight. Some people who have obesity are unable to lose enough weight to improve their health or are unable to keep from regaining weight. In such cases, a doctor may consider adding other treatments, including weight-loss medicines, weight-loss devices, or bariatric surgery.

Experts recommend losing 5 to 10 percent of your body weight within the first 6 months of treatment. [10] If you weigh 200 pounds, this means losing as little as 10 pounds. Losing 5 to 10 percent of your weight may

• help lower your chances of developing health problems related to overweight and obesity
• improve health problems related to overweight and obesity, such as high blood pressure and high cholesterol levels

Healthy eating plan and regular physical activity

Following a healthy eating plan with fewer calories is often the first step in trying to treat overweight and obesity.

People who are overweight or have obesity should also start regular physical activity when they begin their healthy eating plan. Being active may help you use calories. Regular physical activity may help you stay at a healthy weight.

Learn more about healthy eating and physical activity to lose or maintain weight.

Changing your habits

Changing your eating and physical activity habits and lifestyle is difficult, but with a plan, effort, regular support, and patience, you may be able to lose weight and improve your health. The following tips may help you think about ways to lose weight, engage in regular physical activity, and improve health over the long-term.

• Be prepared for setbacks—they are normal. After a setback, like overeating at a family or workplace gathering, try to regroup and focus on getting back to your healthy eating plan as soon as you can. Try to eat only when you’re sitting at your dining room or kitchen table. At work, avoid areas where treats may be available. Track your progress using online food or physical activity trackers, such as the Body Weight Planner, that can help you keep track of the foods you eat, your physical activity, and your weight. These tools may help you stick with it and stay motivated.
• Set goals. Having specific goals can help you stay on track. Rather than “be more active,” set a goal to walk 15 to 30 minutes before work or at lunch on Monday and Friday. If you miss a walk on Monday, pick it up again Tuesday.
• Seek support. Ask for help or encouragement from your family, friends, or health care professionals. You can get support in person, through email or texting, or by talking on the phone. You can also join a support group. Specially trained health professionals can help you change your lifestyle.

Weight-management programs

Some people benefit from a formal weight-management program. In a weight-management program, trained weight-management specialists will design a broad plan just for you and help you carry out your plan. Plans include a lower-calorie diet, increased physical activity, and ways to help you change your habits and stick with them. You may work with the specialists on-site (that is, face-to-face) in individual or group sessions. The specialists may contact you regularly by telephone or internet to help support your plan. Devices such as smartphones, pedometers, and accelerometers may help you track how well you are sticking with your plan.

Some people may also benefit from online weight-management programs or commercial weight-loss programs.

Weight-loss medicines

When healthy eating and physical activity habits are not enough, your doctor may prescribe medicines to treat overweight and obesity.

You should try to stick with your healthy eating plan and continue getting regular physical activity while taking weight-loss medicines.

You may see ads for herbal remedies and dietary supplements that claim to help you lose weight. But many of these claims are not true. Some of these supplements can even have serious side effects. Talk with your doctor before taking any over-the-counter herbal remedies or dietary supplements for the purpose of trying to lose weight.

Weight-loss devices

Your doctor may consider weight-loss devices if you haven’t been able to lose weight or keep from gaining back any weight you lost with other treatments. Because weight-loss devices have only recently been approved, researchers do not have long-term data on their safety and effectiveness. Weight-loss devices include

• Electrical stimulation system. The electrical stimulation system uses a device a surgeon places in your abdomen with laparoscopic surgery. The device blocks nerve activity between your stomach and brain.
• Gastric balloon system. For the gastric balloon system, a doctor places one or two balloons in your stomach through a tube that goes in your mouth. Once the balloons are in your stomach, the surgeon fills them with salt water so they take up more space in your stomach and help you feel fuller.
• Gastric emptying system. A gastric emptying system uses a pump to drain part of the food from your stomach after a meal. The device includes a tube that goes from the inside of your stomach to the outside of your abdomen. About 20 to 30 minutes after eating, you use the pump to drain the food from your stomach through the tube into the toilet.

Bariatric surgery

Bariatric surgery includes several types of operations that help you lose weight by making changes to your digestive system. Bariatric surgery may be an option if you have extreme obesity and haven’t been able to lose enough weight to improve your health or keep from gaining back the weight you lost with other treatments. Bariatric surgery also may be an option at lower levels of obesity if you have serious health problems, such as type 2 diabetes or sleep apnea, related to obesity. Bariatric surgery can improve many of the medical conditions linked to obesity, especially type 2 diabetes.

Special diets

Calorie-restricted diets

Your doctor may recommend a lower-calorie diet such as 1,200 to 1,500 calories a day for women and 1,500 to 1,800 calories a day for men. The calorie level depends on your body weight and physical activity level. A lower calorie diet with a variety of healthy foods will give you the nutrients you need to stay healthy.

Intermittent fasting

Intermittent fasting is another way of reducing food intake that is gaining attention as a strategy for weight loss and health benefits. Alternate-day fasting is one type of intermittent fasting that consists of a “fast day” (eating no calories to one-fourth of caloric needs) alternating with a “fed day,” or a day of unrestricted eating. Researchers have conducted only a few studies of intermittent fasting as a strategy for weight loss. They have no long-term data on the safety and effectiveness of intermittent fasting for long-term weight maintenance.

References

Clinical Trials

The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) and other components of the National Institutes of Health (NIH) conduct and support research into many diseases and conditions.

What are clinical trials for overweight and obesity?

Clinical trials are part of clinical research and at the heart of all medical advances. Clinical trials look at new ways to prevent, detect, or treat disease. Scientists are conducting research to learn more about overweight and obesity, including studies on the role of dietary patterns in obesity development and treatment; novel behavioral, medication, device, and surgical approaches; and other research areas that can tell us more about why people develop obesity or respond to treatment. For example, scientists are conducting clinical trials to

• identify which patients may respond to a specific drug or type of diet
• learn how bacteria in in a person’s gastrointestinal tract may affect his or her risk of becoming overweight or obese
• study how metabolism influences obesity and related health conditions
• investigate how a mother’s weight gain during pregnancy can affect her later health and the health of her baby
• learn how physical activity improves or maintains weight and overall health

Researchers also use clinical trials to look at other aspects of care, such as improving the quality of life for people with chronic illnesses. Find out if clinical trials are right for you.

Watch a video of NIDDK Director Dr. Griffin P. Rodgers explaining the importance of participating in clinical trials.

What clinical trials for overweight and obesity are open?

Clinical trials funded by the NIH or other government agencies focused on treating or managing overweight and obesity that are currently open and recruiting can be viewed at www.ClinicalTrials.gov. This is a curated list of clinical trials, but you can expand or narrow your search to find more clinical trials for overweight and obesity.

What has research taught us about overweight and obesity?

The NIDDK has supported many research projects to learn more about overweight and obesity. Examples include:

• Look AHEAD: Action for Health in Diabetes Trial. This study has shown that people with type 2 diabetes can lose weight and maintain that weight loss through a program of healthy eating and regular physical activity. The study has also shown that weight loss provides added health benefits, such as better physical mobility and quality of life. The trial has been extended to study the long-term results of weight loss through healthy eating and physical activity programs in older adults with type 2 diabetes.
• The Longitudinal Assessment of Bariatric Surgery followed more than 2,400 participants with extreme obesity who underwent bariatric surgery at one of the participating centers. Participants were followed for up to 7 years. Overall, bariatric surgery was safe and had a positive impact on many obesity-related conditions, such as type 2 diabetes and high blood pressure, with good long-term maintenance of the lost weight. However, some risks were identified, such as an increased risk for alcohol use disorders in participants who had gastric bypass surgery.