What Is Obesity?
Doctors define obesity as a chronic (long-lasting) disease that results when have you have excess body fat that puts your health at risk.
It's a complicated condition, and it's about much more than the number on the scale. Carrying extra weight affects the way your body works. These changes influence almost every system in your body. They contribute to diseases like heart disease, diabetes, and cancer.
Obesity is a growing problem in many areas of the world. According to the World Health Organization, more than 4 million people die every year due to obesity or overweight.
Doctors have traditionally used body mass index (BMI) as a tool to determine whether someone is overweight or obese. BMI is a calculation that compares your weight to your height. A BMI of 30 or more is in the obese category. If your BMI is 25 to 29.9, your weight is classified as overweight but not obese.
Measuring your waist is another way to check your risk for weight-related conditions. A waist size over 40 inches (102 centimeters) for men or 35 inches (88 centimeters) for women is considered high.
Some day-to-day symptoms you might have with obesity include:
- Joint pain
- Getting out of breath easily
- A hard time doing physical activities
Types of Obesity
Doctors divide obesity into three classes:
Class I: You're in this category if your BMI is between 30 and 35.
Class II: People in this category have a BMI between 35 and 40.
Class III: In this category, your BMI is 40 or above.
You might have heard the term "morbid obesity" to refer to obesity that's likely to pose serious threats to your health. Doctors formerly used to use this phrase to describe what they now call class III obesity.
Causes of Obesity
Many things contribute to obesity, including your genes, your eating patterns, and how much activity you get. Hormones and your emotions play a role, too. Some illnesses and some medications can also lead to weight gain.
Other things that may be involved include:
- Living in areas where healthy food and safe places to exercise aren't easily available
- Jobs that require you to sit for long periods of time
- Cultural and family preferences for certain foods
- Advertising and marketing that make high-calorie food seem more appealing
Obesity Risk Factors
You're more likely to have obesity if others in your family do. Experts think genes affect your metabolism, your appetite, and how much body fat you tend to store. Also, people around you influence your diet and exercise patterns.
Other risk factors for obesity include:
- Age. Your metabolism (the rate at which your body burns calories) often slows down as you get older. You may become less physically active as well. Menopause can also make you more prone to weight gain.
- Sleep loss. Regularly sleeping less than 7 hours a night causes hormone changes that can boost your appetite and lead you to overeat.
- Pregnancy. It's easy to gain extra weight during pregnancy, and it can be hard to lose it after you give birth.
- Stress. People tend to crave high-calorie foods when they're under stress.
- Certain illnesses and medications. Conditions that can cause weight gain include Cushing, Prader-Willi, and polycystic ovary syndromes. Disabilities and illnesses that make it harder to move around, like arthritis, can contribute, too. Among medications linked to weight gain are some antidepressants, antipsychotics, anti-seizure drugs, beta-blockers, and steroids.
Obesity is very common. More than 40% of adults in the U.S. are considered obese, as are nearly 20% of children.
Among adults in the U.S., rates of obesity by race/ethnicity are:
- Black 50%
- American Indian/Alaska Native 48%
- Hispanic 46%
- White 41%
- Asian 16%
The rates among children are:
- Hispanic 26%
- Black 25%
- White 17%
- Asian 9%
(National obesity rates for American Indian/Alaska Native children were not available.)
Obesity is more common in people at middle age and older. By age, obesity rates are:
- 44% for adults ages 40-59
- 42% for people 60 and up
- 40% of those ages 20-39
Although researchers say that overall rates of obesity are similar for men and women, women are more likely to have severe, or class 3, obesity.
To screen you for obesity, your doctor might talk to you about your health history to learn about your eating and activity patterns, history of weight gain and loss, and more.
They may also do a:
- Physical exam. They'll check vital signs like your blood pressure and heart rate as well as measure your height and weight.
- BMI calculation. Your doctor can use your height and weight to determine your BMI. But because it's based on averages, BMI isn't always an accurate measure of obesity. For example, athletes may have high BMIs although their body-fat levels are low. BMI also doesn't recognize differences in age, gender, or race. Your doctor should take these limitations into account.
- Waist measurement. Your doctor may also measure around your waist to see if you carry extra abdominal fat. This type of fat boosts your risk for health issues like diabetes and heart disease.
- Tests for other conditions. Your doctor may want to check you for weight-related conditions like diabetes and high cholesterol. They may also look for illnesses that could cause weight gain, such as thyroid problems.
There are many treatments for weight loss that can make a big difference to your health and how you feel. Even a small reduction in weight benefits your health.
No matter what type of treatment or program you use, overcoming obesity will require you to change your eating and exercise habits. Your doctor can help you determine what method might be best for you.
You might start with a supervised weight loss and exercise program. Ask your doctor to help you set personal goals and refer you to other professionals who can help. For example, a dietitian can work with you to develop a plan for healthy nutrition, and a physical therapist or trainer can help you move more. A bariatric medicine or weight loss specialist can also be a part of your health care team.
You’ll want to go for steady progress over time and to make lifestyle changes that work for you in the long run. That way you can start losing weight, feel better, and keep the weight off.
Medications for obesity
Along with lifestyle changes, your doctor may recommend prescription medications that decrease your appetite, help you feel full with less food, or help you lose weight in other ways. Keep in mind that these drugs may not work for everyone, and you might regain weight when you stop taking them.
Some drugs the FDA has approved to treat obesity are:
- Benzphetamine (Didrex, Regimex)
- Buproprion-naltrexone (Contrave)
- Cellulose and citric acid (Plenity)
- Diethylpropion (Depletite, Radtue, Tenuate)
- Liraglutide (Saxenda)
- Lisdexamfetamine dimesylate (Vyvanse)
- Orlistat (Alli, Xenical)
- Phendimetrazine (Bontril, Melfiat)
- Phentermine (Adipex, Lomaira, Suprenza)
- Phentermine-topiramate (Qsymia)
- Semaglutide (Wegovy)
- SGLT2 inhibitors with glucagon-like-1 receptor agonists
Doctors may also prescribe certain diabetes drugs, such as tirzepatide (Mounjaro), "off-label" for weight loss even though they're not FDA-approved for that purpose.
Procedures and surgeries for obesity
These procedures change your digestive system to limit how much food you're able to eat or how many calories your body can absorb. Some also affect hormones that play a role in hunger and metabolism.
These procedures may not only help with weight loss but also improve weight-related conditions like type 2 diabetes and heart disease. If you get one of them, you'll still need to adopt healthy lifestyle changes.
Nonsurgical procedures include:
- Endoscopic sleeve gastroplasty, in which a doctor puts stitches in your stomach to reduce how much it can hold.
- Intragastric balloon, in which a balloon is placed into your stomach, then filled with water, to help you feel full sooner.
If you have class 3 obesity, you might be able to get weight loss (bariatric) surgery. These surgeries include:
- Gastric band, in which a band separates your stomach into two smaller compartments
- Gastric bypass, in which the doctor creates a smaller compartment within your stomach and connects it right to your small intestine.
- Gastric sleeve, where the surgeon removes part of your stomach.
- Duodenal switch, which combines gastric sleeve surgery with a procedure that bypasses much of the small intestine.
Therapy for obesity
Cognitive behavioral therapy teaches you behavior changes that can lead to weight loss, such as finding non-food ways to reward yourself or deal with negative emotions. It can also help you learn techniques to reduce stress, which often contributes to overeating.
Alternative treatments for obesity
You can buy many types of herbs and supplements that claim to help with weight loss. But there's little scientific evidence that any of them are effective.
Some research has found that acupuncture or acupressure could have a small effect on weight. These techniques stimulate certain spots on your body to try to boost levels of serotonin, a chemical involved in moods, emotions, and appetite.
There's some evidence that hypnosis might help with weight loss, especially when used together with therapy, diet, and exercise. But not all research into this technique showed the same results.
Obesity Health Disparities
Anyone can have obesity, but it's more common in minority populations. Scientists don't know all of the reasons why. They include genetics as well as family and cultural eating habits. They may also include social aspects like:
- Lack of regular access to good-quality food (food insecurity)
- Unemployment rates
- Easy access to unhealthy foods
- Lack of access to suitable places to exercise
- Lack of access to health care
- Stress and trauma levels
Men have similar rates of obesity no matter what their income level. High-income women are less likely to have it than those with lower incomes. But most women with obesity aren't considered low-income. In the U.S., people living in the Southeast and in rural areas are at higher risk.
Black people are often less likely than others to be diagnosed with obesity, although they have the condition at higher rates.
Some research has found obesity treatments aren't as widely used or as effective for minorities. One study found that after 6 months of behavior therapy for weight loss, Black participants lost less weight than White ones. Certain weight loss drugs, such as orlistat, may be less effective for Black people. Others, like metformin, might not work as well for Hispanic people.
Members of racial and ethnic minority groups tend to lose less weight after weight loss surgery. Men and African-American people are less likely to consider the surgery in the first place.
One of the hardest parts of living with obesity is the stigma that surrounds it. Some people stereotype those with obesity as undisciplined or lazy. You may face discrimination in the workplace and from health care providers. Research suggests that people who have obesity deal with stigma almost every day.
But there are signs of progress. In 2013, the American Medication Association recognized obesity as a chronic disease. And advocacy organizations like the World Obesity Federation and Obesity Action Coalition are bringing attention to the need for change.
Stigma can take a toll on your mental health. There's not a lot of research on obesity stigma. But one study found that people who dealt with it by reframing their bad experiences in a more positive way had less depression and better self-esteem. For example, they focused on good things that have happened to them and reminded themselves that many people like them just as they are.
Complications of Obesity
Extra weight means extra stress on your bones and muscles and less space for your lungs and other organs. It makes your heart and circulation system work harder and increases inflammation in your body. Obesity raises your risk of several other chronic conditions, including:
Type 2 Diabetes
When you have obesity, you're seven times more likely to get type 2 if you're male (or were assigned male gender at birth). You're 12 times more likely to get it if you're female or were assigned female at birth.
Obesity boosts your risk for high cholesterol, blood pressure, and blood sugar as well as inflammation. All these things are risk factors for cardiovascular (heart and blood vessel) conditions like heart attack, stroke, and coronary artery disease.
People with obesity are at higher risk for several types of cancer, including:
With obesity, you're more prone to heartburn and gallbladder disease as well as liver problems like fatty liver disease. Fatty liver disease happens when too much fat builds up in your liver and leads to damage.
Obesity also puts you at higher risk for:
- Sleep apnea
- Pregnancy complications
- Back pain
- Alzheimer's disease
Living With Obesity
While not everyone with obesity has other serious health problems, research shows that it's rare to be both obese and healthy for the long term.
But you don't need to lose a lot of weight to improve your health. You could lower your risk for complications like diabetes and heart failure by 10%-25% by losing just 15-20 pounds.
No single diet is best for weight loss. What works for one person may not work for another. Your doctor or a dietitian can help you find an eating plan that suits your needs and lifestyle. In general, a healthy plan will include:
- Tracking your food intake
- Controlling portions
- Making healthier choices, such as eating more fruits and veggies and less saturated fat and cholesterol
Be wary of fad diets that promise fast weight loss. While you might lose some weight quickly, you're likely to gain it back once you go off the diet. It's better to adopt changes you can live with long-term.
Along with diet, exercise should be part of your weight loss plan. Ask your doctor about what kind of exercise, and how much, is best for you.
Obesity and the medical conditions that can come with it bring extra expenses for treatments, doctor visits, hospitalizations, and more. A 2021 study found that, on average, adults in the U.S. with obesity spent $1,800 more on health care than others.
That doesn't include indirect costs like:
- Missed time and reduced productivity at work
- Disability and insurance expenses
- The costs of weight loss programs
These steps can boost your chances for successfully managing obesity:
- Get support. Tell your family members and friends you need their help making lifestyle changes. Support groups, whether they're nonprofit groups or part of a paid program, can be invaluable. Sharing your experiences with others can help you learn ways to succeed and keep you from getting discouraged. People who join these groups tend to lose more weight than those who do it on their own.
- Write things down. This can help in a few ways. Tracking your food intake and exercise, on paper or in an app, helps you identify and correct unhealthy habits. Journaling about your emotions helps you sort them out and learn what triggers you to eat more. Keeping records of these things makes it easy to share your learnings with doctor or mental health professional.
- Set goals. Make them small and realistic. Instead of vowing to lose 10 pounds in a month, for example, substitute fresh fruit for dessert every night this week. Or take a 10-minute walk after dinner. Once you've conquered one goal, set another.
- Find supportive health care providers who understand obesity is a disease and don't make you feel stigmatized. Ask your doctors to discuss all your options for treating obesity.
- Ease stress. Relaxation techniques like meditation, deep breathing, and stepping away from social media can help you manage stress. That can help you avoid emotional eating and deal with the challenges of obesity.
Obesity and mental health
People with obesity are at higher risk for mood and anxiety disorders. One study found that those with obesity were 55% more likely than others to develop depression during their lifetimes. At the same time, people with depression had a 58% higher chance of obesity.
Some of the reasons for this link include:
- Obesity bias. Discrimination is stressful. It can harm your self-esteem and cause you to take others' negative opinions about your weight to heart (internalize them).
- Negative body image. You may be unhappy with your appearance because it doesn't fit society's norms. You may fear being judged or be embarrassed about your weight.
- Reduced quality of life. Obesity can keep you from doing things you enjoy and cause you to become isolated. Pain and discomfort caused by obesity or related health conditions also contribute to depression.
- Physical changes. Excess fat boosts inflammation in your body. Inflammation helps raise your risk for depression.
- Emotional eating. Many people use food to help them deal with feelings of sadness, stress, or anxiety.
- Depression saps your energy. When you're depressed, you may not feel up to exercise or take part in other healthy lifestyle habits.
Losing weight can help ease depression. But you're not likely to succeed at weight loss when you're feeling sad or stressed. Think about getting treatment for any emotional health issues before you try to overhaul your eating and exercise habits.
Can obesity be cured?
Some obesity experts believe diet and exercise just aren't enough to address obesity. They say our bodies evolved to help us survive periods when food was scarce. So whenever we cut back on calories, our bodies drive us to eat high-calorie foods and gain weight. That's why most weight loss efforts don't succeed in the end.
These experts believe that people with obesity who do manage to lose weight are biologically different from people who've never had obesity. They consider obese people who've lost weight to be in remission rather than cured.
What to expect with obesity
Even moderate obesity (defined as having a BMI of 30-35) can shorten your lifespan by 3 years. Severe obesity (a BMI of 40-50), could take 10 years off your life. That's about the same as a lifetime of smoking.
Weight loss can prevent and sometimes reverse most of the health problems linked to obesity. But losing weight and keeping it off takes commitment and time. While many people can lose some weight with diet and exercise alone, only 10% to 20% are able to maintain the loss for a long time.
Research shows that treatment programs in which you and your doctor work closely together are most effective for long-term weight loss. Weight loss surgery has a high success rate: Some 90% of people who have it are able to lose at least 50% of their extra weight and maintain the loss. And some newer obesity medications are so promising that many doctors consider them game-changers.
It's easier to prevent obesity than to treat it. If obesity runs in your family or you notice you've picked up a few pounds, start taking simple steps to improve your health habits. You might:
- Give up soda in favor of unsweetened soda water.
- Add a 30-minute walk or other workout 5 days a week.
- Stop keeping fatty, sugary foods in the house.
- Limit screen time to an hour a day on most days of the week.
Obesity is not a personal failing. It's a complicated disease that requires lifelong management. Fortunately, more treatment options are available than ever before. Work together with your doctor to get control of your weight and your health.