While overweight and obesity are similar weight-related conditions, they also have differences. If a person has a higher body weight, the doctor will typically evaluate their body mass index (BMI) to detect if they have overweight or obesity.

According to the National Heart, Lung, and Blood Institute, overweight and obesity are prevalent conditions in the United States due to an increase in the size and amount of fat cells in the body.

The cause of overweight and obesity may be multifactorial. This includes eating patterns, lack of sleep, low physical activity, certain medications, genetics, and family history.

Healthcare professionals screen adults for overweight and obesity using body mass index (BMI). This is a measure of body fat based on someone’s height and weight. The formula takes a person’s body weight in kilograms divided by their square of height in meters. It is expressed in units of kg/m².

A doctor will consider other related measures, such as waist circumference, to evaluate a person’s risk of having overweight and obesity.

This article explores the comparison between overweight and obesity.

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While people often use both terms interchangeably, overweight and obesity are two different conditions.

The Centers for Disease Control and Prevention (CDC) notes overweight is a BMI of 25–30, while obesity is a BMI of 30 or higher.

BMI is a calculation of body fat based on a person’s height and weight. However, some studies show it is a poor indicator of a person’s body fat percentage.

It can also be misleading as the measure does not account for a person’s overall body composition. The BMI measurement overlooks bone density, muscle mass, and other considerations.

People can talk with a doctor about other body fat assessment methods for additional information.

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Obesity is considered a chronic health condition. It can lead to an increased risk of serious medical conditions such as heart disease, type 2 diabetes, and certain cancers.

A note about sex and gender

Sex and gender exist on spectrums. This article will use the terms “male,” “female,” or both to refer to sex assigned at birth. Click here to learn more.

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According to a 2016 report by the World Health Organization (WHO):

  • Overweight affects more than 1.9 billion adults ages 18 years and older worldwide.
  • Obesity affects around 650 million adults worldwide.
  • Around 39% of men and 40% of women had overweight.
  • Between 1975 and 2016, the worldwide prevalence rate of obesity tripled.

The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) notes the following overweight and obesity statistics from 2017–2018 in the United States:

  • about 1 in 3 adults, or 30.7%, are overweight
  • over 2 in 5 adults, or 42.4%, have obesity

Learn more about obesity facts and statistics.

The United Kingdom’s National Health Service (NHS) notes that obesity is a complex condition with multiple causes.

Excess calories

If a person continually consumes more high fat or high sugar foods than they burn, the excess calories may cause excess weight gain.

According to the NHS, the following dietary lifestyle may affect a person’s risk of having overweight and obesity:

  • eating large amounts of fast or processed foods
  • consuming large amounts of alcohol
  • drinking a lot of sweetened drinks
  • engaging in “comfort eating”

Sedentary lifestyle

Not getting enough physical activity alongside consuming high calorie, low nutrient foods and beverages can raise a person’s risk of having overweight and obesity.

The CDC recommends 150 minutes of moderate-intensity aerobic activity each week. For instance, this can mean walking for 30 minutes 5 days a week or 75 minutes of vigorous exercise every week.


Genetic variations may increase hunger and food intake, causing obesity. On rare occasions, a specific single gene variant can cause a pattern of inherited obesity within a family.

Research from 2017 suggests that a fat mass and obesity-associated gene — FTO — may play a role in overeating and emotional eating, which is related to obesity.


A 2015 systematic review and meta-analysis showed that some medications may induce weight gain. These include:

Medical conditions

Certain medical conditions can also contribute to weight gain, which can lead to overweight and obesity. These conditions include:

People with overweight or obesity are at increased risk for many serious health conditions. These include:

Learn more about how obesity affects the body.

There are various ways doctors can recommend for treating overweight and obesity. These include lifestyle changes, medications, and surgery.

Lifestyle changes

A healthcare professional can recommend some lifestyle modifications to improve well-being and prevent the severity of overweight or obesity. This may include:

Learn about eating a balanced diet.

Behavioral weight-loss programs

In a behavioral weight-loss program, a healthcare professional or dietitian works closely with a person to identify habits affecting their body weight and develop a personalized lifestyle modification plan to help them lose weight. Typically, this plan is reviewed with the healthcare professional or dietitian every 6 months.


The doctor may prescribe weight loss medications if eating and physical activity are not significantly benefiting a person’s weight loss. Some effective weight loss medications include:


A doctor may prescribe bariatric or weight loss surgery if a person has severe obesity. The NHS notes that the doctor may recommend weight loss surgery as the primary treatment if a person has a BMI of 50 or above.

An individual should discuss all benefits and risks of surgery with a doctor.

The following are some common questions about overweight and obesity.

How does overweight cause obesity?

Usually, being overweight is a risk factor for obesity. If the BMI of a person who is overweight increases to 30 or higher, they will have obesity.

Can you be both overweight and obese?

A person can be both overweight and obese. Obesity is a form of overweight and is where BMI is 30 or higher.

What are the common causes of obesity?

Common causes of obesity include:

  • eating habits
  • sedentary lifestyle
  • genetics

Although overweight and obesity are similar, they are different conditions.

Healthcare professionals diagnose overweight if a person has a BMI range of 25–30 and obesity if they have a BMI of 30 or higher.

According to medical experts, overweight and obesity may be due to several reasons, including low physical activity, high fat and high calorie diet, certain medications or medical conditions, and genetics.

Overweight and obesity may cause health complications such as stroke, osteoarthritis, high blood pressure, and mental health conditions. Treatments include lifestyle changes, medications, and surgery.