Body mass index, known as BMI, is often used to diagnose obesity. To calculate BMI, multiply weight in pounds by 703, divide by height in inches and then divide again by height in inches. Or divide weight in kilograms by height in meters squared. There are several online calculators available that help calculate BMI.

See BMI calculator

Asians with a BMI of 23 or higher may have an increased risk of health problems.

For most people, BMI provides a reasonable estimate of body fat. However, BMI doesn't directly measure body fat. Some people, such as muscular athletes, may have a BMI in the obesity category even though they don't have excess body fat.

Many health care professionals also measure around a person's waist to help guide treatment decisions. This measurement is called a waist circumference. Weight-related health problems are more common in men with a waist circumference over 40 inches (102 centimeters). They're more common in women with a waist measurement over 35 inches (89 centimeters). Body fat percentage is another measurement that may be used during a weight loss program to track progress.

When to see a doctor

If you're concerned about your weight or weight-related health problems, ask your health care professional about obesity management. You and your health care team can evaluate your health risks and discuss your weight-loss options.

Although there are genetic, behavioral, metabolic and hormonal influences on body weight, obesity occurs when you take in more calories than you burn through typical daily activities and exercise. Your body stores these excess calories as fat.

In the United States, most people's diets are too high in calories — often from fast food and high-calorie beverages. People with obesity might eat more calories before feeling full, feel hungry sooner, or eat more due to stress or anxiety.

Many people who live in Western countries now have jobs that are much less physically demanding, so they don't tend to burn as many calories at work. Even daily activities use fewer calories, courtesy of conveniences such as remote controls, escalators, online shopping, and drive-through restaurants and banks.

Obesity often results from a combination of causes and contributing factors:

Family inheritance and influences

The genes you inherit from your parents may affect the amount of body fat you store, and where that fat is distributed. Genetics also may play a role in how efficiently your body converts food into energy, how your body regulates your appetite and how your body burns calories during exercise.

Obesity tends to run in families. That's not just because of the genes they share. Family members also tend to share similar eating and activity habits.

Lifestyle choices

• Unhealthy diet. A diet that's high in calories, lacking in fruits and vegetables, full of fast food, and laden with high-calorie beverages and oversized portions contributes to weight gain.
• Liquid calories. People can drink many calories without feeling full, especially calories from alcohol. Other high-calorie beverages, such as sugared soft drinks, can contribute to weight gain.
• Inactivity. If you have an inactive lifestyle, you can easily take in more calories every day than you burn through exercise and routine daily activities. Looking at computer, tablet and phone screens is inactivity. The number of hours spent in front of a screen is highly associated with weight gain.

Certain diseases and medications

In some people, obesity can be traced to a medical cause, such as hypothyroidism, Cushing syndrome, Prader-Willi syndrome and other conditions. Medical problems, such as arthritis, also can lead to decreased activity, which may result in weight gain.

Some medicines can lead to weight gain if you don't compensate through diet or activity. These medicines include steroids, some antidepressants, anti-seizure medicines, diabetes medicines, antipsychotic medicines and certain beta blockers.

Social and economic issues

Social and economic factors are linked to obesity. It's hard to avoid obesity if you don't have safe areas to walk or exercise. You may not have learned healthy ways of cooking. Or you may not have access to healthier foods. Also, the people you spend time with may influence your weight. You're more likely to develop obesity if you have friends or relatives with obesity.

Age

Obesity can occur at any age, even in young children. But as you age, hormonal changes and a less active lifestyle increase your risk of obesity. The amount of muscle in your body also tends to decrease with age. Lower muscle mass often leads to a decrease in metabolism. These changes also reduce calorie needs and can make it harder to keep off excess weight. If you don't consciously control what you eat and become more physically active as you age, you'll likely gain weight.

Other factors

• Pregnancy. Weight gain is common during pregnancy. Some women find this weight difficult to lose after the baby is born. This weight gain may contribute to the development of obesity in women.
• Quitting smoking. Quitting smoking is often associated with weight gain. And for some, it can lead to enough weight gain to qualify as obesity. Often, this happens as people use food to cope with smoking withdrawal. But overall, quitting smoking is still a greater benefit to your health than is continuing to smoke. Your health care team can help you prevent weight gain after quitting smoking.
• Lack of sleep. Not getting enough sleep can cause changes in hormones that increase appetite. So can getting too much sleep. You also may crave foods high in calories and carbohydrates, which can contribute to weight gain.
• Stress. Many external factors that affect mood and well-being may contribute to obesity. People often seek more high-calorie food during stressful situations.
• Microbiome. The make-up of your gut bacteria is affected by what you eat and may contribute to weight gain or trouble losing weight.

Even if you have one or more of these risk factors, it doesn't mean that you're destined to develop obesity. You can counteract most risk factors through diet, physical activity and exercise. Behavior changes, medicines and procedures for obesity also can help.

People with obesity are more likely to develop a number of potentially serious health problems, including:

• Heart disease and strokes. Obesity makes you more likely to have high blood pressure and unhealthy cholesterol levels, which are risk factors for heart disease and strokes.
• Type 2 diabetes. Obesity can affect the way the body uses insulin to control blood sugar levels. This raises the risk of insulin resistance and diabetes.
• Certain cancers. Obesity may increase the risk of cancer of the uterus, cervix, endometrium, ovary, breast, colon, rectum, esophagus, liver, gallbladder, pancreas, kidney and prostate.
• Digestive problems. Obesity increases the likelihood of developing heartburn, gallbladder disease and liver problems.
• Sleep apnea. People with obesity are more likely to have sleep apnea, a potentially serious disorder in which breathing repeatedly stops and starts during sleep.
• Osteoarthritis. Obesity increases the stress placed on weight-bearing joints. It also promotes inflammation, which includes swelling, pain and a feeling of heat within the body. These factors may lead to complications such as osteoarthritis.
• Fatty liver disease. Obesity increases the risk of fatty liver disease, a condition that happens due to excessive fat deposit in the liver. In some cases, this can lead to serious liver damage, known as liver cirrhosis.
• Severe COVID-19 symptoms. Obesity increases the risk of developing severe symptoms if you become infected with the virus that causes coronavirus disease 2019, known as COVID-19. People who have severe cases of COVID-19 may need treatment in intensive care units or even mechanical assistance to breathe.

Quality of life

Obesity can diminish the overall quality of life. You may not be able to do physical activities that you used to enjoy. You may avoid public places. People with obesity may even encounter discrimination.

Other weight-related issues that may affect your quality of life include:

• Depression.
• Disability.
• Shame and guilt.
• Social isolation.
• Lower work achievement.

To diagnose obesity, your health care professional may perform a physical exam and recommend some tests.

These exams and tests often include:

• Taking your health history. Your health care team may review your weight history, weight-loss efforts, physical activity and exercise habits. You also may talk about your eating patterns and appetite control. Your health care professional may ask about other conditions you've had, medicines you take, your stress levels and other issues about your health. They may also review your family's health history to see if you may be more likely to have certain conditions.
• A general physical exam. This includes measuring your height; checking vital signs, such as heart rate, blood pressure and temperature; listening to your heart and lungs; and examining your abdomen.
• Calculating your BMI. Your health care professional checks your body mass index, called BMI. A BMI of 30 or higher is considered obesity. Numbers higher than 30 increase health risks even more. Have your BMI checked at least once a year. This can help pinpoint your overall health risks and what treatments may be right for you.
• Measuring your waist size. The distance around your waist is known as the circumference. Fat stored around the waist, sometimes called visceral fat or abdominal fat, may further increase the risk of heart disease and diabetes. Women with a waist that measures more than 35 inches (89 centimeters) and men with a waist that's more than 40 inches (102 centimeters) around may have more health risks than do people with smaller waist measurements. Like the BMI measurement, waist circumference should be checked at least once a year.
• Checking for other health problems. If you have known health problems, your health care team will evaluate them. Your health care professional also will check for other possible health problems, such as high blood pressure, high cholesterol, underactive thyroid, liver problems and diabetes.

Gathering this information will help you and your health care team choose the type of treatment that will work best for you.

The goal of obesity treatment is to reach and stay at a healthy weight. This improves overall health and lowers the risk of developing complications related to obesity.

You may need to work with a team of health professionals — including a dietitian, behavioral counselor or an obesity specialist — to help you understand and make changes in your eating and activity habits.

The first treatment goal is usually a modest weight loss — 5% to 10% of your total weight. That means that if you weigh 200 pounds (91 kilograms), you'd need to lose only about 10 to 20 pounds (4.5 to 9 kilograms) for your health to begin to improve. But the more weight you lose, the greater the benefits.

All weight-loss programs require that you change your eating habits and get more active. The treatment methods that are right for you depend on your weight, your overall health and your willingness to participate in a weight-loss plan.

Dietary changes

Reducing calories and practicing healthier eating habits are key to overcoming obesity. Although you may lose weight quickly at first, steady weight loss over the long term is considered the safest way to lose weight. It's also the best way to keep weight off permanently.

There is no best weight-loss diet. Choose one that includes healthy foods that you feel will work for you. Dietary changes to treat obesity include:

• Cutting calories. The key to weight loss is reducing how many calories you take in. The first step is to review your typical eating and drinking habits. You can see how many calories you usually consume and where you can cut back. You and your health care professional can decide how many calories you need to take in each day to lose weight. A typical amount is 1,200 to 1,500 calories for women and 1,500 to 1,800 for men.
• Feeling full on less. Some foods — such as desserts, candies, fats and processed foods — contain a lot of calories for a small portion. In contrast, fruits and vegetables provide a larger portion size with fewer calories. By eating larger portions of foods that have fewer calories, you can reduce hunger pangs and take in fewer calories. You also may feel better about your meal, which contributes to how satisfied you feel overall.
• Making healthier choices. To make your overall diet healthier, eat more plant-based foods. These include fruits, vegetables and whole grains. Also emphasize lean sources of protein — such as beans, lentils and soy — and lean meats. If you like fish, try to include fish twice a week. Limit salt and added sugar. Eat small amounts of fats, and make sure they come from heart-healthy sources, such as olive, canola and nut oils.
• Restricting certain foods. Certain diets limit the amount of a particular food group, such as high-carbohydrate or full-fat foods. Ask your health care professional which diet plans are effective and which might be helpful for you. Drinking sugar-sweetened beverages is a sure way to consume more calories than you intended. Limiting these drinks or eliminating them altogether is a good place to start cutting calories.
• Meal replacements. These plans suggest replacing one or two meals each day with their products — such as low-calorie shakes or meal bars — and eating healthy snacks. Then you have a healthy, balanced third meal that's low in fat and calories. In the short term, this type of diet can help you lose weight. But these diets likely won't teach you how to change your overall lifestyle. So you may have to stay on the diet if you want to keep your weight off.

Be wary of quick fixes. You may be tempted by fad diets that promise fast and easy weight loss. But the reality is that there are no magic foods or quick fixes. Fad diets may help in the short term, but the long-term results don't appear to be any better than other diets.

Similarly, you may lose weight on a crash diet, but you're likely to regain it when you stop the diet. To lose weight — and keep it off — you must adopt healthy-eating habits that you can maintain over time.

Exercise and activity

Getting more physical activity or exercise is an essential part of obesity treatment:

• Exercise. People with obesity need to get at least 150 minutes a week of moderate-intensity physical activity. This can help prevent further weight gain or maintain the loss of a modest amount of weight. You'll probably need to gradually increase the amount you exercise as your endurance and fitness improve.
• Keep moving. Even though regular aerobic exercise is the most efficient way to burn calories and shed excess weight, any extra movement helps burn calories. For example, park farther from store entrances and take the stairs instead of the elevator. A pedometer can track how many steps you take over the course of a day. Many people try to reach 10,000 steps every day. Gradually increase the number of steps you take daily to reach your goal.

Behavior changes

A behavior modification program can help you make lifestyle changes to lose weight and keep it off. Steps to take include looking at your current habits to find out what factors, stresses or situations may have contributed to your obesity.

• Counseling. Talking with a mental health professional can help address emotional and behavioral issues related to eating. Therapy can help you understand why you overeat and learn healthy ways to cope with anxiety. You also can learn how to monitor your diet and activity, understand eating triggers, and cope with food cravings. Counseling can be one-on-one or in a group.
• Support groups. You can find friendship and understanding in support groups where others share similar challenges with obesity. Check with your health care team, local hospitals or commercial weight-loss programs for support groups in your area.

Weight-loss medicines

Weight-loss medicines are meant to be used along with diet, exercise and behavior changes, not instead of them. Before selecting a medication for you, your health care professional will consider your health history, as well as possible side effects.

The most commonly used medications approved by the U.S. Food and Drug Administration (FDA) for the treatment of obesity include:

• Bupropion-naltrexone (Contrave).
• Liraglutide (Saxenda).
• Orlistat (Alli, Xenical).
• Phentermine-topiramate (Qsymia).
• Semaglutide (Ozempic, Rybelsus, Wegovy).

Weight-loss medicines may not work for everyone, and the effects may wane over time. When you stop taking a weight-loss medicine, you may regain much or all of the weight you lost.

Endoscopic procedures for weight loss

These types of procedures don't require any cuts, also called incisions, in the skin. After you are under anesthesia, flexible tubes and tools are inserted through the mouth and down the throat into the stomach. Common procedures include:

• Endoscopic sleeve gastroplasty. This procedure involves placing stitches in the stomach to reduce the amount of food and liquid the stomach can hold at one time. Over time, eating and drinking less helps the average person lose weight.
• Intragastric balloon for weight loss. In this procedure, you have a small balloon placed into the stomach. The balloon is then filled with water to reduce the amount of space in the stomach, so you'll feel full eating less food. Intragastric balloons are left in place for up to 6 months and are then removed using an endoscope. At that time, a new balloon may be placed, or not, depending on the plan determined by you and your health care team.

Weight-loss surgery

Also known as bariatric surgery, weight-loss surgery limits how much food you can eat. Some procedures also limit the amount of calories and nutrients you can absorb. But this also can result in nutritional and vitamin deficiencies.

Common weight-loss surgeries include:

• Adjustable gastric banding. In this surgery, an inflatable band placed around the outside of the stomach divides it into two pouches. The surgeon pulls the band tight, like a belt, to create a narrow pathway between the two pouches. The band keeps the opening from getting bigger. The band often stays in place permanently.
• Gastric bypass surgery. In gastric bypass, also called Roux-en-Y (roo-en-wy) gastric bypass, the surgeon creates a small pouch at the top of the stomach. The small intestine is then cut a short distance below the main stomach and connected to the new pouch. Food and liquid flow directly from the pouch into this part of the intestine, bypassing most of the stomach.
• Gastric sleeve. In this surgery, part of the stomach is removed, creating a smaller reservoir for food. It's a less complicated surgery than gastric bypass.

Weight-loss success after surgery depends on your commitment to making lifelong changes in your eating and exercise habits.

Other treatments

Other treatments for obesity include:

• Hydrogels. Available by prescription, these edible capsules contain tiny particles that absorb water and get bigger in the stomach, to help you feel full. The capsules are taken before meals and are passed through the intestines as stool.
• Vagal nerve blockade. This involves implanting a device under the skin in the stomach area. The device sends electrical pulses to a nerve in that area, called the abdominal vagus nerve. This nerve tells the brain when the stomach feels empty or full.
• Gastric aspirate. In this procedure, a tube is placed through the abdomen into the stomach. A portion of the stomach contents are drained out after each meal.

Your effort to overcome obesity is more likely to be successful if you follow strategies at home along with your formal treatment plan. These can include:

• Learning about your condition. Education about obesity can help you learn more about why you developed obesity and what you can do about it. You may feel more empowered to take control and stick to your treatment plan. Read reputable self-help books and consider talking about them with your health care professional or therapist.
• Setting realistic goals. When you have to lose a lot of weight, you may set goals that are unrealistic, such as trying to lose too much too fast. Don't set yourself up for failure. Set daily or weekly goals for exercise and weight loss. Make small changes in your diet instead of attempting drastic changes that you're not likely to stick with for the long haul.
• Sticking to your treatment plan. Changing a lifestyle you may have lived with for many years can be hard to do. Be honest with your doctor, therapist or other health care professionals if you find your activity or eating goals slipping. You can work together to come up with new ideas or new approaches.
• Enlisting support. Get your family and friends on board with your weight-loss goals. Surround yourself with people who will support you and help you, not sabotage your efforts. Make sure they understand how important weight loss is to your health. You also might want to join a weight-loss support group.
• Keeping a record. Keep a food and activity log. This record can help you remain accountable for your eating and exercise habits. You can discover things that may be holding you back. You also might see what works well for you. You can use your log to track other important health parameters such as blood pressure, cholesterol levels and overall fitness.

Many dietary supplements that promise to help you shed weight quickly are available. The long-term effectiveness and safety of these products are often questionable.

Talk to your health care professional or therapist about improving your coping skills. Consider these tips to cope with obesity and your weight-loss efforts:

• Journal. Write in a journal to express pain, anger, fear or other emotions.
• Connect. Don't become isolated. Try to participate in regular activities and get together with family or friends periodically.
• Join. Join a support group so that you can connect with others facing similar challenges.
• Focus. Stay focused on your goals. Overcoming obesity is an ongoing process. Stay motivated by keeping your goals in mind. Remind yourself that you're responsible for managing your condition and working toward your goals.
• Relax. Learn relaxation and stress management. Learning to recognize stress and developing stress management and relaxation skills can help you gain control of unhealthy eating habits.

Talking to your health care professional openly and honestly about your weight concerns is one of the best things you can do for your health. In some cases, you may be referred to an obesity specialist — if one is available in your area. You also may be referred to a behavioral counselor or dietitian.

What you can do

Being an active participant in your care is important. One way to do this is by preparing for your appointment. Think about your needs and goals for treatment. Also, write down a list of questions to ask. These questions may include:

• What eating or activity habits are likely contributing to my health concerns and weight gain?
• What can I do about the challenges I face in managing my weight?
• Do I have other health problems that are caused by obesity?
• Should I see a dietitian?
• Should I see a behavioral counselor with expertise in weight management?
• What are the treatment options for obesity and my other health problems?
• Is weight-loss surgery or another intervention an option for me?

Be sure to let your health care team know about any medical conditions you have and about any medicines, vitamins or supplements that you take.

What to expect from your doctor

During your appointment, your health care professional is likely to ask you a number of questions about your weight, eating, activity, mood and thoughts, and any symptoms you might have. You may be asked questions such as:

• How much did you weigh in high school?
• What life events may have been associated with weight gain?
• What, when and how much do you eat in a typical day?
• How much activity do you get in a typical day?
• During what periods of your life did you gain weight?
• What are the factors that you believe affect your weight?
• How is your daily life affected by your weight?
• What diets or treatments have you tried to lose weight?
• What are your weight-loss goals?
• Are you ready to make changes in your lifestyle to lose weight?
• What do you think might prevent you from losing weight?

What you can do in the meantime

If you have time before your scheduled appointment, you can get ready for the appointment by keeping a diet diary for two weeks before the appointment. You also can record how many steps you take in a day by using a step counter, called a pedometer.

And you can begin to make choices that will help you start to lose weight, including:

• Making healthy changes in your diet. Include more fruits, vegetables and whole grains in your diet. Begin to reduce portion sizes.
• Increasing your activity level. Try to get up and move around your home more often. Start gradually if you aren't in good shape or aren't used to exercising. Even a 10-minute daily walk can help. If you have any health conditions or are over a certain age — over 40 for men and over 50 for women — wait until you've talked to your health care professional before you start a new exercise program.