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Obesity is a condition of excessive body fat that increases the risk for other conditions such as diabetes and heart disease. Fat is how the body stores extra calories that were eaten but not used. Obesity treatment usually involves restricting the calories eaten or creating negative calorie balance

Our evidence-based analysis on obesity features 50 unique references to scientific papers.

Research analysis led by and reviewed by the Examine team.
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Summary of Obesity

What is obesity?

Obesity means having more body fat than what's calculated to be healthy. Obesity increases the risk of diabetes, heart disease, stroke, arthritis, and some cancers. In people with obesity, losing even 5-10% of the total weight can delay or prevent some of these other conditions.[1]

How is obesity diagnosed?

Obesity is defined as having a body mass index (BMI) of greater than or equal to 30 kilograms per meters squared (kg/m2; “meters” meaning a person’s height). More specifically, a person with:[2]

  • A BMI of 24-29.9 is “overweight”

  • A BMI of 30-34.9 has “class I obesity”

  • A BMI of 35-39.9 has “class II obesity”

  • And a BMI of 40 or higher has “class III obesity”

What are some of the main medical treatments for obesity?

The primary treatment for obesity in patients without other health conditions is lifestyle modifications (i.e., changes to diet and exercise); sometimes, weight loss medications are also used. If lifestyle modifications do not work after trying for a long time, or if the person has class II or III obesity with additional chronic conditions like heart disease or diabetes, then bariatric surgery may be considered.[2]

Have any supplements been studied for obesity?

Many dietary supplements and dietary ingredients have been studied for weight loss. In a recent meta-analysis of 67 randomized trials, the dietary ingredients chitosan, glucomannan, and conjugated linoleic acid were shown to help reduce weight by 1-1.9 kilograms. Other ingredients commonly studied for weight loss include green tea extract, green coffee, bitter orange, and Garcinia cambogia. Evidence about their effects is limited.[3]

What's the connection between diet and obesity?

Diet is central to both the development and the management of obesity. Obesity occurs after a prolonged duration of consuming more energy than is used. The mainstay of dietary interventions for treating obesity involves calorie restriction. A commonly used approach includes limiting daily calorie intake to 1200–1500 kilocalories (calories adjusted to a person’s weight) for women and 1500–1800 kilocalories for men. Another approach is eating a diet with a 500-750 kilocalorie deficit. Many different types of diets have been used for weight loss; the diet that will be most beneficial over time will vary from person to person, and adherence to the diet is crucial.[2]

Are there any other treatments for obesity?

Physical activity and behavioral therapies are important in the treatment of obesity. Increasing physical activity increases calories burned and works in tandem with calorie-restricting diets for obesity. Engaging in 200-300 minutes of physical activity per week is recommended for those with obesity. Behavioral therapy usually involves regular self-monitoring of food intake, physical activity, and changes to weight.[2]

What causes obesity?

Obesity happens after a prolonged time of eating more calories than what is needed and used by the body. Extra calories are stored as fat. The factors that determine caloric need differ for each person. Factors that affect weight include genetic makeup, overeating, eating high-fat foods, and not being physically active.[1]

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Frequently Asked Questions and Articles on Obesity

How valid is BMI as a measure of health and obesity?
BMI is not a highly accurate measure of obesity. That being said, it can be useful as a complementary datum. BMI has a high rate of false negatives, particularly among females, with nearly half of obese people being classified as normal or overweight in some studies. The amount of false positives, on the other hand, is surprisingly small: less than 5% in men and 1% in women, according to one study.
Can hypothyroidism lead to fat gain?
Yes, a less active thyroid will reduce metabolic rate and can cause some weight gain. It is not a lot of weight gain though, and a subactive thyroid is not an excuse for obesity (if hypothyroidic, please see a doctor for medication; it burns fat)
Can you be Healthy and Obese?
Not optimally healthy when morbidly obese, but health parameters could be improved (to a degree) independent of weight loss with further benefits inducing weight loss
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