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Obesity is characterized by excess body fat; it is currently considered to be at epidemic levels in the United States and many other countries around the world. Studies have shown that being obese is associated with an increased risk of death from causes such as hypertension, stroke, heart disease, and other conditions.

Obesity is typically measured by body mass index, or BMI, a value calculated as weight in kilograms divided by height in meters squared. According to the Centers for Disease Control:

  • A BMI of 25 to 30 is within the overweight range
  • A BMI is 30 or higher is within the obesity range
  • BMI of 40 or higher is considered severe obesity

According to the CDC, children with a BMI at or above the 85th percentile are considered overweight, while those with a BMI at or above the 95th percentile are considered obese.

The CDC also reported that the adult obesity rate is at about 42.4 percent, and the rate is at about 19.3 percent for children and adolescents. Rates of obesity have gone up from 12 to almost 40 percent of the population since 1991. The percentage of youths who are overweight has more than doubled in the past 20 years. Eighteen percent of children and adolescents between 2 and 19 years old are now considered obese.

Research has shown that being overweight is significantly associated with an increased risk of death from hypertension, dyslipidemia (high cholesterol), type 2 diabetes, stroke, osteoarthritis, coronary heart disease, gallbladder disease, sleep apnea and respiratory problems, and endometrial, breast, prostate, and colon cancers.


    MI is intended to measure total body fat in relation to someone’s frame, as an excess amount is linked to the risk of disease and death. BMI is considered valid in most cases, but it has been criticized; it may overestimate body fat in those with a muscular build, and it may underestimate body fat in older persons or others without much muscle mass. Not everyone who is technically obese suffers from health problems, and combining BMI and waist circumference with information about additional risk factors can give someone an idea of their risk for developing obesity-associated diseases.

    According to the guidelines from the National Institutes of Health's Heart, Lung, and Blood Institute, an individual’s waist circumference (which can be determined by placing a measuring tape snugly around the waist) is a good indicator of their abdominal fat. A waist measurement of more than 40 inches in men and more than 35 inches in women is a strong predictor of risk for heart disease and other illnesses. Additional inches are associated with increased risk.

    For obese or overweight people who have two or more of the risk factors listed above, the NIH recommends weight loss. Even a small amount of weight loss (such as 5 or 10 percent of current weight) lowers someone’s chance of developing diseases associated with obesity. Patients who are overweight or obese—but who have a low waist measurement and only one or none of the above risk factors—may only need to prevent further weight gain rather than lose weight.

    Anyone who is concerned about their weight and health should ask their doctor to evaluate their BMI, waist measurement, and other risk factors for heart disease. He or she can assess the level of risk and determine whether that individual should lose weight or make any lifestyle changes.

    How is obesity assessed?

    Three key measures are used in assessing obesity:

    • Body mass index (BMI): A measure of weight in relation to height

    • Waist circumference: A measure of abdominal fat

    • Risk factors for diseases and conditions associated with obesity

    What risk factors are associated with obesity?

    According to the NIH, other risk factors that are associated with obesity that can have a negative impact on health include: 

    • High blood pressure (hypertension)

    • High LDL ("bad" cholesterol)

    • Low HDL ("good" cholesterol)

    • High triglycerides

    • High blood glucose (sugar)

    • Family history of premature heart disease

    • Physical inactivity or a sedentary lifestyle

    • Cigarette smoking

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    An individual’s weight is the result of many overlapping factors, including environment, family history and genetics, metabolism, and behavior. Genes strongly influence a person's weight, which is why vulnerability to weight gain and obesity tends to run in families. But other factors in weight gain, such as exercise habits and dietary choices, are more likely to be under an individual’s control.

    Many who live in developed countries are not regularly and consistently physically active. According to the Department of Health and Human Services, less than 5 percent of adults are physically active for 30 or more minutes a day, and only one third of adults get the recommended amount of weekly exercise. Only one in three children exercise daily. People who are physically inactive are more likely to gain weight.

    One reason for such inactive lifestyles is an increasingly sedentary culture taking hold in many highly developed countries. Many jobs or at-home activities no longer require intense physical demands; whether working or engaging in leisure, many children and adults spend much of their time in front of TVs, computers, or on their phones. Those living in developed nations also typically rely on cars for transportation instead of walking or biking. Other environmental challenges may include a lack of time for physical activity or lack of access to recreational space or healthy foods. Research has also found an association between obesity and insufficient sleep.


    To manage obesity and reduce weight, a combination of a healthy diet and regular exercise appears to work better than either one alone. Sticking to a weight reduction program can be challenging and often requires long-term commitment and support from family and friends.

    When dieting, the main goal should be to learn new, healthy ways of eating and make them a part of an everyday routine. Working with a doctor and nutritionist to set realistic, safe daily calorie counts is the best way to assure both weight loss and good nutrition. A doctor can determine the healthiest rate for an individual to lose weight, while a nutritionist can teach them about healthy food choices, appropriate portion sizes, and new ways to prepare food.

    Dropping pounds slowly and steadily appears to be the most effective way to keep them off, and even modest weight loss can improve someone’s health. Patience is essential, as weight loss and maintenance is a slow process that requires significant commitment.

    Some people lose weight on their own; others prefer the support of a structured program. The National Heart, Lung, and Blood Institute advises anyone considering a weight-loss program to determine whether it teaches lasting habit and lifestyle changes and long-term strategies for dealing with weight and whether it is staffed by qualified health professionals.

    Quick weight-loss methods do not often lead to lasting results. Evidence shows that relying on diet aids like drinks, prepackaged foods or pills don't work over the long term. No matter how much weight a person wishes to lose, modest goals and a slow pace can increase their chances of losing the weight and keeping it off.

    Physical Activity

    Exercise is an integral part of any weight loss and weight maintenance plan, as well as general health. It also reduces the risk of cardiovascular disease and diabetes, beyond what weight reduction achieves alone.

    Exercise can be done all at one time or intermittently over a day. For those who aren’t accustomed to physical activity, initial activities may be light, such as walking or swimming at a slow pace. One can increase activity by undertaking frequent, less strenuous exercises, such as walking up and down the stairs instead of using the elevator. Once some progress has been made, many find they are eventually able to engage in more strenuous activities.


    Weight-loss surgery may be an option for those who are very obese and have not been able to lose weight through diet and exercise. However, these surgeries are not a "quick fix" for obesity. An individual must still be committed to diet and exercise after the surgery. Discuss this option with a doctor.

    What percentage of weight should a person lose?

    According to the NIH expert panel on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults: The initial goal of weight-loss therapy should be to reduce body weight by about 10 percent from baseline. For the first six months, weight loss should be approximately one to two pounds per week. If necessary, the patient can continue to lose more weight. 

    Will reducing dietary fat alone enough to lose weight?

    The NIH panel on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults recommends that reducing dietary fat alone is not enough to lose weight; certain kinds of fat are beneficial and necessary for a healthy body to function. However, reducing dietary fat along with reducing dietary carbohydrates can help reduce calories, which can help with weight loss.

    Center for Disease Control
    National Heart, Lung and Blood Institute
    National Institutes of Health, National Library of Medicine
    U.S. Department of Health and Human Services
    National Institute of Diabetes & Digestive & Kidney Diseases
    Last updated: 11/15/2021