Energy imbalances can cause overweight and obesity. An energy imbalance means that your energy IN does not equal your energy OUT. This energy is measured in calories. Energy IN is the amount of calories you get from food and drinks. Energy OUT is the amount of calories that your body uses for things such as breathing, digesting, being physically active, and regulating body temperature.
Overweight and obesity develop over time when you take in more calories than you use, or when energy IN is more than your energy OUT. This type of energy imbalance causes your body to store fat.
Your body uses certain nutrients such as carbohydrates or sugars, proteins, and fats from the foods you eat to:
The amount of energy that your body gets from the food you eat depends on the type of foods you eat, how the food is prepared, and how long it has been since you last ate.
The body has three types of fat tissue—white, brown, and beige—that it uses to fuel itself, regulate its temperature in response to cold, and store energy for future use. Learn about the role of each fat type in maintaining energy balance in the body.
Some genetic syndromes and endocrine disorders can cause overweight or obesity.
Several genetic syndromes are associated with overweight and obesity, including the following.
The study of these genetic syndromes has helped researchers understand obesity.
Because the endocrine system produces hormones that help maintain energy balances in the body, the following endocrine disorders or tumor affecting the endocrine system can cause overweight and obesity.
Medicines such as antipsychotics, antidepressants, antiepileptics, and antihyperglycemics can cause weight gain and lead to overweight and obesity.
Talk to your doctor if you notice weight gain while you are using one of these medicines. Ask if there are other forms of the same medicine or other medicines that can treat your medical condition, but have less of an effect on your weight. Do not stop taking the medicine without talking to your doctor.
Several parts of your body, such as your stomach, intestines, pancreas, and fat tissue, use hormones to control how your brain decides if you are hungry or full. Some of these hormones are insulin, leptin, glucagon-like peptide (GLP-1), peptide YY, and ghrelin.
There are many risk factors for overweight and obesity. Some risk factors can be changed, such as unhealthy lifestyle habits and environments. Other risk factors, such as age, family history and genetics, race and ethnicity, and sex, cannot be changed. Heathy lifestyle changes can decrease your risk for developing overweight and obesity.
Lack of physical activity, unhealthy eating patterns, not enough sleep, and high amounts of stress can increase your risk for overweight and obesity.
Lack of physical activity due to high amounts of TV, computer, videogame or other screen usage has been associated with a high body mass index. Healthy lifestyle changes, such as being physically active and reducing screen time, can help you aim for a healthy weight.
Some unhealthy eating behaviors can increase your risk for overweight and obesity.
Visit Heart-healthy eating for more information about healthy eating patterns.
Many studies have seen a high BMI in people who do not get enough sleep. Some studies have seen a relationship between sleep and the way our bodies use nutrients for energy and how lack of sleep can affect hormones that control hunger urges. Visit our Sleep Deprivation and Deficiency Health Topic for more information about lack of sleep.
Acute stress and chronic stress affect the brain and trigger the production of hormones, such as cortisol, that control our energy balances and hunger urges. Acute stress can trigger hormone changes that make you not want to eat. If the stress becomes chronic, hormone changes can make you eat more and store more fat.
Childhood obesity remains a serious problem in the United States, and some populations are more at risk for childhood obesity than others. The risk of unhealthy weight gain increases as you age. Adults who have a healthy BMI often start to gain weight in young adulthood and continue to gain weight until 60 to 65 years old, when they tend to start losing weight.
Many environmental factors can increase your risk for overweight and obesity:
Genetic studies have found that overweight and obesity can run in families, so it is possible that our genes or DNA can cause these conditions. Research studies have found that certain DNA elements are associated with obesity.
Did you know obesity can change your DNA and the DNA you pass on to your children? Learn more about these DNA changes.
Overweight and obesity is highly prevalent in some racial and ethnic minority groups. Rates of obesity in American adults are highest in blacks, followed by Hispanics, then whites. This is true for men or women. While Asian men and women have the lowest rates of unhealthy BMIs, they may have high amounts of unhealthy fat in the abdomen. Samoans may be at risk for overweight and obesity because they may carry a DNA variant that is associated with increased BMI but not with common obesity-related complications.
In the United States, obesity is more common in black or Hispanic women than in black or Hispanic men. A person’s sex may also affect the way the body stores fat. For example, women tend to store less unhealthy fat in the abdomen than men do.
Overweight and obesity is also common in women with polycystic ovary syndrome (PCOS). This is an endocrine condition that causes large ovaries and prevents proper ovulation, which can reduce fertility.
To screen for overweight and obesity, doctors measure BMI using calculations that depend on whether you are a child or an adult. After reading the information below, talk to your doctor or your child’s doctor to determine if you or your child has a high or increasing BMI.
If your BMI indicates you are getting close to being overweight, or if you have certain risk factors, your doctor may recommend you adopt healthy lifestyle changes to prevent you from becoming overweight and obese. Changes include healthy eating, being physically active, aiming for a healthy weight, and getting healthy amounts of sleep. Read healthy lifestyle changes for more information
There are no specific symptoms of overweight and obesity. The signs of overweight and obesity include a high body mass index (BMI) and an unhealthy body fat distribution that can be estimated by measuring your waist circumference. Obesity can cause complications in many parts of your body.
Another sign of overweight and obesity is having an unhealthy body fat distribution. Fatty tissue is found in different parts of your body and has many functions. Having an increased waist circumference suggests that you have increased amounts of fat in your abdomen. An increased waist circumference is a sign of obesity and can increase your risk for obesity-related complications.
Did you know that fatty tissue has different functions depending on its location in your body?
Visceral fat is the fatty tissue inside of your abdomen and organs. While we do not know what causes the body to create and store visceral fat, it is known that this type of fat interferes with the body’s endocrine and immune systems and promotes chronic inflammation and contributes to obesity-related complications.
Obesity may cause the following complications:
Did you know inflammation is thought to play a role in the onset of certain obesity-related complications?
Researchers now know more about visceral fat, which is deep in the abdomen of overweight and obese patients. Visceral fat releases factors that promote inflammation. Chronic obesity-related inflammation is thought to lead toinsulin resistance and diabetes, changes in the liver or non-alcoholic fatty acid liver disease, and cancers. More research is needed to understand what triggers inflammation in some obese patients and to find new treatments.
Your doctor may diagnose overweight and obesity based on your medical history, physical exams that confirm you have a high body mass index (BMI) and possibly a high waist circumference, and tests to rule out other medical conditions.
To diagnose overweight and obesity, doctors measure BMI using calculations that depend on whether you are a child or an adult.
Your doctor will ask about your eating and physical activity habits, family history, and will see if you have other risk factors Your doctor may ask if you have any other signs or symptoms. This information can help determine if you have other conditions that may be causing you to be overweight or obese or if you have complications from being overweight or obese.
During your physical exam, your doctor will measure your weight and height to calculate your BMI. Your doctor may also measure your waist circumference to estimate the amount of unhealthy fat in your abdomen. In adults, a waist circumference over 35 inches for women who are not pregnant or 40 inches for men can help diagnose obesity and assess risk of future complications. If you are of South Asian or Central and South American descent, your doctor may use smaller waist circumference values to diagnose your obesity. People from these backgrounds often don’t show signs of a large waist circumference even though they may have unhealthy amounts of fat deep in their abdomens and may be diagnosed with obesity. Visit Assessing Your Weight for more information.
Read Living With for more information about why it is important to monitor your waist circumference to assess your risk for complications.
Your doctor may order some of the following tests to identify medical conditions that may be causing your overweight and obesity.
Treatment for overweight and obesity depends on the cause and severity of your condition. Possible treatments include healthy lifestyle changes, behavioral weight-loss treatment programs, medicines, and possibly surgery. You may need treatments for any complications that you have.
To help you aim for and maintain a healthy weight, your doctor may recommend that you adopt lifelong healthy lifestyle changes.
Making lifelong healthy lifestyle changes, such as heart-healthy eating and physical activity, can help you modify your energy balance to help you aim for and maintain a healthy weight. For example:
Your doctor may recommend you enroll in individual or group behavioral weight-loss programs to treat your overweight and obesity. In these programs, a trained healthcare professional will customize a weight-loss plan for you. This plan will include a moderately-reduced calorie diet, physical activity goals, and behavioral strategies to help you make and maintain these lifestyle changes. Read Living With for more information about required follow-up for these behavioral treatment programs.
Did you know your brain’s pleasure and reward centers can be stimulated by food and the act of eating, making it harder to change eating patterns and lose weight?
Researchers know that our brains can become patterned so that we feel pleasure or reward from eating. This can make us unconsciously crave food so our bodies feel that sense of pleasure. It can also make it hard to change our eating patterns, lose weight, or maintain a healthy weight. Researchers are studying whether cognitive behavioral therapies can be an effective treatment for overweight and obesity by retraining the brain to not associate pleasure with food and the act of eating.
When healthy lifestyle changes are not enough, your doctor may treat your overweight and obesity with FDA-approved medicines. These medicines work in the following parts of your body.
Weight loss medicines are not recommended as a single treatment for weight loss. These medicines can help you lose weight but when combined with lifestyle changes may result in greater weight loss. Some of these medicines should not be used if you have certain conditions or are taking certain medicines. Also, these medicines have side effects. Talk to your doctor if you are pregnant, planning to get pregnant, breast feeding, or have a family history of cardiovascular diseases such as high blood pressure, heart attack, or stroke.
Some patients with obesity do not respond to healthy lifestyle changes and medicines. When these patients develop certain obesity-related complications, they may be eligible for the following surgeries.
Talk to your doctor to learn more about the benefits and risks of each type of surgery. Possible complications include bleeding, infection, internal rupture of sutures, or even death. Read gastric bypass surgery for more information.
Interested in learning why these surgeries lead to weight loss in some patients?
First, these surgeries reduce the amount of food stored in the stomach and the amount of calories your body can take in. This can help your body restore energy balance. Second, these surgeries change the levels of certain hormones and the way the brain responds to these hormones to control hunger urges. After surgery, some people are less interested in eating or they prefer to eat healthier foods. In some cases, genetic differences may affect how much weight loss patients experience after bariatric surgery.
If you have been diagnosed with overweight and obesity, it is important that you continue your treatment. Read about tips to help you aim for a healthy weight, the benefit of finding and continuing a behavioral weight-loss program, and ways your doctor may monitor if your condition is stable, worsening, or improving and assess your risk for complications.
Changing lifestyle habits takes time and patience. Follow these tips to help you maintain the healthy lifestyle changes your doctor recommended to aim for a healthy weight.
Visit More Information for important NHLBI resources to help you aim for a healthy weight.
Some people find it is easier to aim and maintain a healthy weight when they have support from a weight-loss specialist or other individuals who also are trying to lose weight. Behavioral weight-loss programs can provide this support, and they can help you set goals that are specific to your needs. Your weight-loss specialist usually reviews or modifies your goals every six months based on your progress and overall health.
When you are choosing a behavioral weight-loss program, you may want to consider whether the program should:
When selecting a program, you may want to ask about:
You should visit your health care provider periodically to monitor for possible complications, which if left untreated can be life-threatening. Your doctor may do any of the following to monitor your condition.
The NHLBI is part of the U.S. Department of Health and Human Services’ National Institutes of Health (NIH)—the nation’s biomedical research agency that makes important scientific discovery to improve health and save lives. We are committed to advancing science and translating discoveries into clinical practice to promote the prevention and treatment of heart, lung, blood, and sleep disorders including overweight and obesity. Learn about the current and future NHLBI efforts to improve health through research and scientific discovery.
Learn about the following ways NHLBI continues to translate research and science into improved health for people who are overweight or obese.
Learn about some of the pioneering research contributions we have made over the years that have improved clinical care.
In support of our mission, we are committed to advancing overweight and obesity research in part through the following ways.
Learn more about the exciting research areas we are exploring about overweight and obesity.
Participate in NHLBI Clinical Trials will discuss some of our overweight and obesity clinical trials that are open.
The National Heart, Lung, and Blood Institute (NHLBI) leads or sponsors many studies aimed at preventing, diagnosing, and treating heart, lung, blood, and sleep disorders.
To learn more about clinical trials at the NIH Clinical Center or to talk to someone about a study that might fit your needs, call the Office of Patient Recruitment 800-411-1222.
After reading our overweight and obesity Health Topic, you may be interested in additional information found in the following resources.