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Condition Basics

What is obesity?

Obesity means having an unhealthy amount of body fat. This puts your health in danger. It can lead to other health problems, such as type 2 diabetes and high blood pressure.

What causes it?

Obesity is complex. You gain weight when you take in more calories than you burn off. But other things can affect your weight. These things may include your genetic makeup, what and how you eat, how active you are, what health problems you may have, and what medicines you may take.

How is it diagnosed?

To know if your weight is in the obesity range, your doctor looks at your body mass index (BMI) and waist size.

BMI is a number that is calculated from your weight and your height. To figure out your BMI for yourself, you can use an online tool, such as on the National Institutes of Health website.

If your BMI is 30.0 or higher, it falls within the obesity range. Keep in mind that BMI and waist size are only guides. They are not tools to determine your ideal body weight.

How is obesity treated?

The best way to lose weight is to eat less and move more. Little steps mean a lot. Losing just 10% of your body weight can make a difference in your health.

Some people take medicines or have surgery to help them lose weight. Your doctor may also suggest counseling. If you use food to cope with depression, loneliness, anxiety, or boredom, you can learn new skills to deal with those feelings.

You'll have the most success if you make a long-term plan with your doctor. Your first goal will likely be to improve your health, not to reach an ideal weight.

Can you take medicines or have surgery to lose weight?

If you have a BMI in a certain range and have not been able to lose weight with diet and exercise, medicine or surgery may be an option for you.

If you have a BMI of at least 30.0 (or a BMI of at least 27.0 and another health problem related to your weight), ask your doctor about weight-loss medicines. They work by making you feel less hungry, making you feel full more quickly, or changing how you digest fat. Medicines are used along with diet changes and more physical activity to help you make lasting changes.

If you have a BMI of 40.0 or more (or a BMI of 35.0 or more and another health problem related to your weight), your doctor may talk with you about surgery. Weight-loss surgery has risks, and you will need to work with your doctor to compare the risk of having obesity with the risks of surgery.

With any option you choose, you will still need to eat a healthy diet and get regular exercise.

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Obesity is complex. You gain weight when you take in more calories than you burn off. But other things can affect your weight. These things include:

What and how you eat.
Eating unhealthy foods and overeating are easy in our culture today. Many things influence eating behavior, including emotions, habits, and access to food.
How active you are.
Modern conveniences—such as elevators, cars, and the remote control for the television—cut activity out of our lives. Being active helps you stay fit. When you're fit, you burn more calories, even when you're resting.
Your genetic makeup.
Your genetic makeup has a very big effect on your weight. It affects:
  • The rate at which your body uses energy (calories) when at rest, called your basal metabolic rate. Some people are born with higher basic metabolic rates than others. They naturally burn more calories than other people.
    • Regular physical activity can raise your metabolic rate.
    • Very low-calorie diets will lower your metabolic rate. A lower metabolic rate makes it easier to gain weight, because you don't burn calories as fast.
  • Your body signals, such as your appetite and feeling hungry or full.
  • Your fat distribution. You can't change where your body stores fat. Typically, men store fat in the belly (abdomen) while women store more in the hips and thighs. As women age, more fat is stored in the abdomen.
Medicines or health problems.
Some conditions and medicines may also cause weight gain. Examples include having Cushing's syndrome or hypothyroidism and taking certain antidepressants or corticosteroids.

What Increases Your Risk

If one of your parents is obese, you're more likely to be overweight too. But other things can also put you at risk.

Your friends and family.
If they eat a lot of snack foods high in saturated fat, eat at odd times, and skip meals, you probably will too. And if they are not physically active, you may not be either.
Low self-esteem.
Being overweight may lower your self-esteem and lead to eating as a way to comfort yourself. Dieting a lot without success also can affect your self-esteem.
Emotional concerns.
Stress, anxiety, or illnesses such as depression or chronic pain can lead to overeating. People sometimes eat to calm themselves or to avoid dealing with unpleasant tasks or situations. Others may eat to cope with negative emotions.
Distressing events can contribute to overeating. Examples include sexual, physical, or emotional abuse and marital or family problems.
Alcohol is very high in calories.

What Happens

Obesity can raise your risk for certain health problems. These may include type 2 diabetes, high blood pressure, coronary artery disease (CAD), and stroke. If you have healthier habits or lose weight, you can lower your risk for these conditions.

Learn more


Exams and Tests

Doctors use a tool called BMI (body mass index) to see if your weight could be unhealthy. If your BMI is 30 or higher, your weight may be putting your health in danger. If you are Asian, your health may be at risk at 27.5 or higher.footnote 1

Other tests include measuring your waist and percentage of body fat. Your doctor may also want to know your basal metabolic rate (BMR) to find out how many calories you need each day.

If you are concerned about your child's weight

If you are concerned that your child is—or could become—overweight, talk with your doctor. Doctors use growth charts or the body mass index (BMI) to check a child's weight. Your doctor also may ask about your child's diet and family medical history. Your child also may have a physical exam and some tests.

Learn more

Treatment Overview

The best way to lose weight is to eat less and move more. Little steps mean a lot. Losing just 10% of your body weight can make a difference in your health.

You'll have the most success if you make a long-term plan with your doctor. Your first goal will likely be to improve your health, not to reach an ideal weight.

Some people take medicines or have surgery to help them lose weight. Your doctor may also suggest counseling. If you use food to cope with depression, loneliness, anxiety, or boredom, you can learn new skills to deal with those feelings.

You might want to try weight-loss medicines or have weight-loss surgery if:

  • You do not lose weight after you have tried healthy eating and more activity for 6 months.
  • You keep gaining weight.
  • You have lost weight several times only to regain it.
  • Your doctor is concerned about a health problem related to obesity, such as heart disease or diabetes.

Lifestyle changes

Most people have more success when they make small changes, one step at a time. For example, you might eat an extra piece of fruit or add more vegetables to your meals.

One of the best ways to increase your activity is by walking.


Medicine may help you lose a small amount of weight. But without permanent changes in eating and exercise habits, most people gain weight again after they stop taking the medicine.


After surgery, you will need to make big, lifelong changes in how you eat, including smaller portions and different foods.

Weight-Loss Strategies and Programs

If you're thinking about losing weight, it can be hard to know where to start. Your doctor can help you set up a weight loss plan that best meets your needs. You may want to take a class on nutrition or exercise, or you could join a weight loss support group. If you have questions about how to make changes to your eating or exercise habits, ask your doctor about seeing a registered dietitian or an exercise specialist.

It can be a big challenge to lose weight. But you don't have to make huge changes at once. Make small changes, and stick with them. When those changes become habit, add a few more changes.

If you don't think you're ready to make changes right now, try to pick a date in the future. Make an appointment to see your doctor to discuss whether the time is right for you to start a plan.

Making a weight-loss plan

You might have heard that a certain diet plan helped another person lose weight. But that doesn't mean that it will work for you.

It's very hard to stay on a diet that includes lots of big changes in your eating habits. If you want to get to a healthy weight and stay there, making healthy lifestyle changes will often work better than dieting. These steps can help.

  • Make a plan for change.

    Work with your doctor to create a plan that's right for you.

  • See a dietitian.

    He or she can show you how to make healthy changes in your eating habits.

  • Be active.

    Part of reaching a healthy weight is being physically active.

  • Manage stress.

    Having a lot of stress in your life can make it hard to focus on making healthy changes to your daily habits.

  • Track your food and activity.

    You are likely to do better at losing weight if you keep track of what you eat and what you do.

Tips for staying with your plan

Be ready. Choose to start during a time when there are few events like holidays, social events, and high-stress periods. These events might trigger slip-ups.

Decide on your first few steps. Most people have more success when they make small changes, one step at a time. For example, you might switch a daily candy bar to a piece of fruit, walk 10 minutes more, or add more vegetables to a meal.

Line up your support people. Make sure you're not going to be alone as you make this change. Connect with people who understand how important it is to you. Ask family members and friends for help in keeping with your plan. And think about who could make it harder for you, and how to handle them.

Try tracking. People who keep track of what they eat, feel, and do are better at losing weight. Try writing down things like:

  • What and how much you eat.
  • How you feel before and after each meal.
  • Details about each meal (like eating out or at home, eating alone, or with friends or family).
  • What you do to be active.

Look and plan. As you track, look for patterns that you may want to change. Take note of:

  • When you eat and whether you skip meals.
  • How often you eat out.
  • How many fruits and vegetables you eat.
  • When you eat beyond feeling full.
  • When and why you eat for reasons other than being hungry.

When you stray from your plan, don't get upset. Figure out what made you slip up and how you can fix it.

Weight-loss programs

If you decide to join a weight-loss program, ask some questions: Does the program provide counseling? Is the staff qualified? What can you eat? What percentage of people get to the maintenance phase of the program? What are the risks? What is the total cost?

Learn more


Tips for Getting to a Healthy Weight

  • Improve your eating habits. You'll be more successful if you work on changing one eating habit at a time. All foods, if eaten in moderation, can be part of healthy eating. Remember to:
    • Eat a variety of foods from each food group. Include grains, vegetables, fruits, dairy, and protein foods.
    • Limit foods high in fat, sugar, and calories.
    • Eat slowly. And don't do anything else, such as watch TV, while you are eating.
    • Pay attention to portion sizes. Put your food on a smaller plate.
    • Plan your meals ahead of time. You'll be less likely to grab something that's not as healthy.
  • Get active. Regular activity can help you feel better, have more energy, and burn more calories. If you haven't been active, start slowly. Start with at least 30 minutes of moderate activity on most days of the week. Then gradually increase the amount of activity. Try for 60 or 90 minutes a day, at least 5 days a week. There are a lot of ways to fit activity into your life. You can:
    • Walk or bike to the store. Or walk with a friend, or walk the dog.
    • Mow the lawn, rake leaves, shovel snow, or do some gardening.
    • Use the stairs instead of the elevator, at least for a few floors.
  • Change your thinking. Your thoughts have a lot to do with how you feel and what you do. When you're trying to reach a healthy weight, changing how you think about certain things may help. Here are some ideas:
    • Don't compare yourself to others. Healthy bodies come in all shapes and sizes.
    • Pay attention to how hungry or full you feel. When you eat, be aware of why you're eating and how much you're eating.
    • Focus on improving your health instead of dieting. Dieting almost never works over the long term.
  • Ask your doctor about other health professionals who can help you reach a healthy weight.
    • A dietitian can help you make healthy changes in your diet.
    • An exercise specialist or personal trainer can help you develop a safe and effective exercise program.
    • A counselor or psychiatrist can help you cope with issues such as depression, anxiety, or family problems that can make it hard to focus on reaching a healthy weight.
  • Get support from your family, your doctor, your friends, a support group—and support yourself.

Learn more



Doctors prescribe weight loss medicines for people who are obese or overweight and have other health problems, such as high blood pressure or diabetes. These medicines may help some people who haven't been able to lose weight with diet and exercise.

Medicine choices

Doctors may prescribe medicines to help in losing weight. These medicines include:

Bupropion/naltrexone (Contrave).
This medicine may reduce your appetite. It may help you avoid overeating.
Liraglutide (Saxenda).
You take this medicine as a shot once a day. It may help you eat less.
Orlistat (Xenical).
Orlistat prevents some of the fat calories you eat from being absorbed in your intestines. Prescription-strength orlistat is the only weight-loss medicine that is approved for children. It is meant to be used only in children over the age of 12. It's also available without a prescription under the brand name Alli. Alli is half as strong as Xenical. It should not be used by anyone under the age of 18.
Phentermine/topiramate (Qsymia).
This medicine combines the drugs phentermine and topiramate. Taking it once a day can help you eat less.

How well medicines work

Depending on the medicine they take, some people are able to lose from 4 to 24 pounds. Weight-loss medicines are used along with healthy eating and being more active. Without those lifestyle changes, you will gain the weight back if you stop taking the medicine.

Over-the-counter weight-loss products

Over-the-counter weight-loss products include appetite suppressants and water-loss pills. Many of these have never been proved effective. And those that are effective often come with warnings.

Learn more


Bariatric surgery is surgery to help you lose weight. This type of surgery is only used for people who are very overweight and have not been able to lose weight with diet and exercise.

This surgery makes the stomach smaller. Some types of surgery also change the connection between your stomach and intestines.

Having weight-loss surgery is a big step. After surgery, you'll need to make new, lifelong changes in how you eat and drink.

This type of surgery may be considered if your body mass index (BMI) is at least 40, or if it's at least 35 and you have other weight-related health problems. If your BMI is 35 or higher, surgery may be done if you have tried for at least 6 months to lose weight.

Learn more




  1. Purnell JQ (2011). Obesity. In EG Nabel, ed., ACP Medicine, section 6, chap. 12. Hamilton, ON: BC Decker.


Current as of: August 25, 2022

Author: Healthwise Staff
Medical Review:
E. Gregory Thompson MD - Internal Medicine
Kathleen Romito MD - Family Medicine
Martin J. Gabica MD - Family Medicine
Adam Husney MD - Family Medicine
Rhonda O'Brien MS, RD, CDE - Certified Diabetes Educator

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