By Mayo Clinic Staff

Obesity is defined as having an excessive amount of body fat. Obesity is more than just a cosmetic concern, though. It increases your risk of diseases and health problems such as diabetes and high blood pressure.

Doctors often use a formula based on your height and weight - called the body mass index (BMI) - to determine if you are obese. Adults with a BMI of 30 or higher are considered obese. Extreme obesity, also called severe obesity or morbid obesity, occurs when you have a BMI of 40 or more. With morbid obesity, you are especially likely to have serious health problems.


Weight status

Below 18.5


18.5 - 24.9


25.0 - 29.9


30.0 and higher


Today, about one in three American adults is considered to be obese, but obesity is also becoming an increasing health problem globally. The good news is that even modest weight loss can improve or prevent the health problems associated with obesity.


Symptoms associated with obesity can include:

  • Difficulty sleeping
  • Snoring
  • Sleep apnea
  • Pain in your back or joints
  • Excessive sweating
  • Always feeling hot
  • Rashes or infection in folds of your skin
  • Feeling out of breath with minor exertion
  • Daytime sleepiness or fatigue
  • Depression

When to see a doctor

If you have symptoms associated with obesity such as the ones above, see your doctor or health care provider. You and your doctor can discuss your weight-loss options. Even modest weight loss can improve or prevent problems related to obesity. Weight loss is usually possible through dietary changes, increased physical activity and behavior changes. In some cases, prescription medications or weight-loss surgery may be options.


Although there are genetic and hormonal influences on body weight, the bottom line is that obesity occurs when you take in more calories than you burn through exercise and normal daily activities. Your body stores these excess calories as fat. Obesity usually results from a combination of causes and contributing factors, including:

  • Inactivity. If you're not very active, you don't burn as many calories. Unfortunately, today most adults spend most of their day sitting, whether at home, at work - or during leisure activities. With a sedentary lifestyle, you can easily take in more calories every day than you burn off through exercise or normal daily - activities. Watching too much television is one of the biggest contributors to a sedentary lifestyle and weight gain.
  • Unhealthy diet and eating habits. Having a diet that's high in calories, eating fast food, skipping breakfast, eating most of your calories at night, consuming - high-calorie drinks and eating oversized portions all contribute to weight gain.
  • Pregnancy. During pregnancy a woman's weight necessarily increases. 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.
  • Lack of sleep. Getting less than seven hours of sleep a night can cause changes in hormones that increase your appetite. You may also crave foods high in calories - and carbohydrates, which can contribute to weight gain.
  • Certain medications. Some medications can lead to weight gain if you don't compensate through diet or activity. These medications include some antidepressants, - anti-seizure medications, diabetes medications, antipsychotic medications, steroids and beta blockers.
  • Medical problems. Obesity can sometimes be traced to a medical cause, such as Prader-Willi syndrome, Cushing's syndrome, polycystic ovary syndrome, and other - diseases and conditions. Some medical problems, such as arthritis, can lead to decreased activity, which may result in weight gain. A low metabolism is unlikely to - cause obesity, as is having low thyroid function.

Risk Factors

Factors that may increase your risk of obesity include:

  • Genetics. Your genes 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 and how your body burns calories during exercise.
  • Family history. Obesity tends to run in families. That's not just because of genetics. Family members tend to have similar eating, lifestyle and activity habits. If - one or both of your parents are obese, your risk of being obese is increased.
  • 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. In addition, - the amount of muscle in your body tends to decrease with age. This lower muscle mass 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 decrease your caloric intake as you age, you'll likely gain weight.
  • Quitting smoking. Quitting smoking is often associated with weight gain. And for some, it can lead to a weight gain of as much as several pounds a week for several - months, which can sometimes lead to obesity.
  • Social and economic issues. Certain social and economic issues may be linked to obesity. You may lack access to safe areas to exercise, you may not have been taught - healthy ways of cooking, or you may not have the financial means to buy fresh fruits and vegetables or foods that aren't processed and packaged. In addition, some - studies show that your social networks influence your weight - you're more likely to become obese if you have obese friends or relatives.
  • Even if you have one or more of these risk factors, it doesn't mean that you're destined to become obese. You can counteract most risk factors through diet, - physical activity and exercise, and behavior changes.


If you're obese, you're more likely to develop a number of potentially serious health problems, including:

  • Blood (fat) lipid abnormalities
  • Cancer, including cancer of the uterus, cervix, ovaries, breast, colon, rectum and prostate
  • Depression
  • Gallbladder disease
  • Gynecological problems, such as infertility and irregular periods
  • Heart disease
  • High blood pressure
  • Metabolic syndrome
  • Nonalcoholic fatty liver disease
  • Osteoarthritis
  • Skin problems, such as intertrigo and impaired wound healing
  • Sleep apnea
  • Stroke
  • Type 2 diabetes

Quality of life When you're obese, your overall quality of life may be lower, too. You may not be able to get around or to perform normal daily activities as well as you'd like. You may have trouble participating in family activities. You may avoid public places. You may even encounter discrimination.

Other issues that may affect your quality of life include:

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