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Obesity: Medical Definition, Causes, Types, Solutions

Jun 08, 2023

When a person is diagnosed with obesity, they have excessive fat and are above the weight considered "healthy" for their height. Healthcare providers often use body mass index (BMI) to distinguish between adults who are overweight (BMI between 25 and 30) and those with obesity (BMI of 30 or above). Having these conditions is associated with several health risks, including:

Obesity is common. A wide-ranging survey of data from 2017 to 2018 found over 40% of American adults had it, with the numbers increasing.

This article will discuss the definition of "obesity," its causes and effects, and how it's treated and managed.

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Clinically, obesity is often defined in terms of the BMI. It's determined by measuring a person's weight in kilograms (kg) and dividing it by their height in meters squared (m2). After determining a person's BMI, a healthcare provider may refer to their weight in one of the following four categories:

Assessing weight status with BMI is flawed and dated. This measure excludes relevant factors, such as body composition, ethnicity, sex, race, and age. Its widespread use continues predominantly because it's of no cost and can quickly determine a person's potential health status and outcomes.

Healthcare providers may use other tests alongside BMI to screen for obesity, including:

Research has shown these methods to be as or more effective in determining obesity-related risks. A recent review comparing BMI to other measures found all forms comparable but noted that ultrasound might miss some instances of obesity, especially among older adults.

The review also noted that, while some studies have found few differences among the screening tools, others reported weight circumference and weight-to-hip ratio were more reliable than BMI at predicting obesity and related disease risk.

Obesity rates have been rising among American children and teenagers. In a health data survey from 2017 to 2018, nearly 1 in 5 (19.3%) of those between ages 2 and 19 had obesity. Childhood obesity increases the lifetime risk of developing type 2 diabetes and heart disease. Moreover, children and teens with obesity are more prone to anxiety, depression, and problems with self-esteem.

The human body requires calories (energy) from food and drink to function. Obesity and weight gain occur due to energy imbalances, when a person consumes more calories than their body uses over a period of time.

If a person doesn't immediately use the calories they consume, the body stores them for long-term use as a type of fat known as triglycerides. Body fat increases as triglycerides accumulate from excess calories.

While excess calories directly cause obesity, various health issues and behaviors can increase a person's risk of developing obesity, including:

Obesity causes a range of symptoms and can lead to dangerous conditions, so in 2013, the American Medical Association recommended that obesity be considered a disease that should be medically managed.

Notably, some people who develop obesity don't have symptoms. However, in adults, this condition is often characterized by:

In children and teenagers, obesity commonly causes symptoms, including:

Obesity increases the risk of developing additional complications and health conditions, including the following:

Managing obesity involves various approaches, from lifestyle changes to medications to surgery.

The cornerstone of any weight management program is dietary changes. Talk to a healthcare provider before making any significant changes.

Your medical provider may refer you to a registered dietitian (RD) or registered dietitian nutritionist (RDN), who will work with you to create a personalized healthy eating plan. Strategies include:

When incorporating a new eating plan, it's essential to make the changes gradually. A healthy diet should be paired with other lifestyle changes to ensure results.

Increasing physical activity is essential for weight loss. How much exercise do you need? Every week Adults should aim for 150 to 300 minutes of moderate-intensity activity weekly. Activities could include:

Those who prefer high-intensity aerobic exercise should aim for 75 to 150 minutes weekly. Examples of high-intensity exercise include:

As with diet, talk to a healthcare provider before making changes. Start small and scale up if you don't currently focus on fitness.

Research has shown that not getting enough sleep can increase the chances of developing obesity. Adults should aim for seven to eight hours of uninterrupted rest every night; children and adolescents require more. Follow a consistent sleep schedule to improve sleep quality.

Behavioral weight loss programs in individual or group settings are an excellent obesity management tool. Trained professionals, such as weight loss counselors, RDs and RDNs, exercise specialists, or psychiatrists, assist people with customized diet and exercise plans to manage the condition. They may also provide behavioral strategies to ensure consistent and long-lasting results.

A healthcare provider may prescribe medications if diet, exercise, or behavioral programs are not yielding results. These medications reduce appetite, block food absorption in the intestines, or stimulate the pancreas to release insulin.

Examples of medications prescribed to treat obesity include:

These are not meant as standalone treatments; they work alongside other methods to promote results.

Specialized devices to reduce the amount of food an individual can digest can promote weight loss. Two such devices approved by the Food and Drug Administration (FDA) are:

A healthcare provider may recommend weight loss surgery for difficult-to-manage cases of obesity that pose significant health risks. There are three primary approaches:

If left unmanaged, obesity can significantly impact a person's health, reduce their quality of life, and lead to complications. Research has shown that all-cause mortality—death due to associated conditions, such as cancer, type 2 diabetes, and heart diseases—is significantly elevated in people with this condition.

In addition to the physical health impact, there's a mental health burden to living with obesity. According to one cross-sectional analysis, people with obesity are 25% more likely to have depression, anxiety, or other mental health conditions. Additionally, those with this condition are more likely to face social stigmatization and discrimination in employment and education.

Many resources are available to manage obesity and reduce the risk of complications. If you are trying to manage weight and make changes to your lifestyle, there are several resources for support, including:

National Institute of Diabetes and Digestive and Kidney Diseases. Overweight & obesity statistics.

Centers for Disease Control and Prevention. Health effects of overweight and obesity.

Centers for Disease Control and Prevention. About adult BMI.

National Institutes of Health. How are obesity and overweight diagnosed?.

Centers for Disease Control and Prevention. Assessing your weight.

Khanna D, Peltzer C, Kahar P, Parmar MS. Body Mass Index (BMI): A screening tool analysis. Cureus. 2022;14(2):e22119. doi:10.7759/cureus.22119

National Heart, Lung, and Blood Institute. Childhood obesity.

National Heart, Lung, and Blood Institute. Obesity: Causes and risk factors.

Kyle TK, Dhurandhar EJ, Allison DB. Regarding obesity as a disease: Evolving policies and their implications. Endocrinol Metab Clin North Am. 2016;45(3):511-520. doi:10.1016/j.ecl.2016.04.004

National Health Service. Obesity overview.

Sarwer DB, Polonsky HM. The psychosocial burden of obesity. Endocrinol Metab Clin North Am. 2016;45(3):677-688. doi:10.1016/j.ecl.2016.04.016

Ansari S, Haboubi H, Haboubi N. Adult obesity complications: Challenges and clinical impact. Ther Adv Endocrinol Metab. 2020;11:2042018820934955

Centers for Disease Control and Prevention. Healthy eating for a healthy weight.

National Heart, Lung, and Blood Institute. Get regular physical activity.

National Heart, Lung, and Blood Institute. Overweight and obesity: Treatment.

Centers for Disease Control and Prevention. Health effects of overweight and obesity.

National Heart, Lung, and Blood Institute. Overweight and obesity: treatment.

National Institutes of Health. How are obesity and overweight diagnosed?.

By Mark GurarieMark Gurarie is a freelance writer, editor, and adjunct lecturer of writing composition at George Washington University.

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