Overweight vs. Obesity: Key Differences and Health Risks Explained
Health ConditionsObesity

Overweight vs. Obesity: Understanding the Differences and Health Impacts

Overweight vs. Obesity: Understanding the Differences and Health Impacts
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Updated on April 21, 2026
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Nearly 3 out of 4 Americans are overweight (32 percent) or have obesity (40 percent).

 For years, both have been diagnosed using body mass index (BMI), which assesses a person’s body weight in proportion to their height. People with higher BMIs can have a higher risk of weight-related health conditions, such as high blood pressure, type 2 diabetes, and heart disease.

That said, doctors are now looking beyond BMI to diagnose people who are overweight and have obesity by considering additional factors, such as their waist circumference and where they store excess fat. Where excess fat is stored can have a significant impact on a person’s risk of weight-related health issues, says Francisco Lopez-Jimenez, MD, director of the cardiometabolic program at Mayo Clinic in Rochester, Minnesota.

“Fat stored around the abdomen is more strongly linked to heart disease and diabetes than fat in other areas,” says Dr. Lopez-Jimenez. “Waist-based measurements are a simple way to estimate this risk.”

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What Is BMI and How Does It Measure Obesity?

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What Are the Definitions of Overweight and Obesity?

Doctors rely on BMI to determine whether people are overweight or have obesity, but it’s becoming just one of several measurements clinicians can use to diagnose these chronic conditions.

The Role of BMI

Adults with a BMI of 18.5 to 24.9 are considered at a healthy weight. An adult who is 5 feet 9 inches tall has a BMI in this range if they weigh 125 to 168 pounds.

Individuals with a BMI of 25 to 29.9 are considered overweight. An adult who is 5 feet 9 inches tall has a BMI in the overweight range if they weigh 169 to 202 pounds.

Those with a BMI of 30 or higher have obesity. An adult who is 5 feet 9 inches tall has obesity if they weigh 203 pounds or more.

BMI ranges for overweight and obesity differ for people of Asian and South Asian descent, with overweight characterized by a BMI of 23 to 27.4 and obesity characterized by a BMI of 27.5 or higher.

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What is Waist-to-Hip Ratio?

Obesity physician Kimberly Gudzune, MD, demonstrates how to measure an accurate waist-to-hip ratio, and explains why it is an effective alternative to BMI (body mass index) for identifying risk of weight-related health outcomes.

Why BMI Is No Longer the Only Metric

The trouble with BMI is that it doesn’t always identify people who have health risks linked to excess body weight. For this reason, the American Medical Association encourages physicians to look beyond BMI to get a more complete picture of a patient’s risk.

Since BMI relies solely on height and weight measurements, a person who has a lot of lean muscle mass (which adds weight) can have the same BMI as someone who has more body fat mass.

 What’s more, the original formula doesn’t consider that body fat naturally varies based on a person’s sex, race, and ethnicity, nor does it account for other factors like genetic risk or bone density that can influence the potential for a certain weight to lead to health issues in a particular person.

Moving Toward Better Measurements

Other measurements can help provide a complete assessment of whether you have an unhealthy weight. Waist circumference is one way to measure excess fat around the midsection, which tends to carry a higher risk of conditions like heart disease and diabetes than excess fat stored on the hips.

A waist circumference of more than 35 inches for women or more than 40 inches for men can indicate an increased risk of weight-related health issues and can be used to consider whether you’re overweight or have obesity.

Major global bodies, such as the World Health Organization and the International Diabetes Federation, recognize lower waist circumference thresholds for Asian populations due to their higher metabolic risk at lower visceral fat levels.

A dual-energy X-ray absorptiometry (DEXA) scan is another helpful measurement tool that provides a precise body composition analysis including your body fat percentage, lean body mass percentage, and overall fat distribution. DEXA scans, sometimes called DXA scans, can give a much more comprehensive picture of whether you’re at a healthy weight than BMI alone.

Key Differences: Is Obesity a Disease?

A higher BMI and more body fat is the most obvious difference between overweight and obesity, but the definitions and causes of the two chronic conditions can also differ.

People become overweight when the amount of energy (calories) they take in is greater than the amount of energy they burn, causing them to gain weight. People are considered overweight when they have excess body fat and a BMI in the overweight range.

Obesity, on the other hand, is a chronic, relapsing disease. It’s a more severe form of excess body fat and weight that can change how the body works and increases the risk of related diseases. Obesity is also a multifactorial condition. A combination of genetic, environmental, and socioeconomic factors (which can include one’s level of family support, loneliness, work stress, and the ability to afford healthy food) causes it.

Overweight
Obesity

BMI of 25.0–29.9

BMI of 30+

Caused by taking in more energy than used

A chronic disease caused by a combination of genetic, environmental, and socioeconomic factors

Increases risk of heart disease, high blood pressure, type 2 diabetes, some cancers, and other health conditions

Severely increases risk of heart disease, high blood pressure, type 2 diabetes, some cancers, and other health conditions

Treated with diet, exercise, and sometimes prescription weight loss medications

Treated with diet, exercise, prescription weight loss medications, and sometimes bariatric surgery

How Weight Impacts Long-Term Health

“Obesity isn’t just excess weight,” says Christopher McGowan, MD, an obesity medicine specialist and the senior vice president at Everself, a weight care company with locations throughout the United States. “It’s a chronic inflammatory disease affecting the entire body.”

The Role of Inflammation

The trouble with overweight and obesity isn’t just that one carries excess body fat, but rather the type of fat that accumulates.

Visceral adipose tissue, the belly fat that can appear as you gain weight, develops deep in the abdomen and encases vital organs, including the kidneys, liver, and pancreas. Visceral adipose tissue is metabolically active. It causes inflammation throughout the body that increases one’s risk of weight-related health issues, like diabetes and heart disease.

Systemic Impact

As a person’s weight increases, so does their risk of a wide range of weight-related issues, including:

  • Heart Disease Excess fat can affect blood vessels and lead to high blood pressure. It also contributes to other heart disease risk factors, such as high cholesterol, type 2 diabetes, and sleep apnea.
  • Type 2 Diabetes Excess fat makes cells more resistant to the effects of insulin, a hormone that moves sugar (glucose) from the bloodstream into cells. It also damages beta cells in the pancreas, which are responsible for making insulin. As a result, blood sugar levels rise.
  • Obstructive Sleep Apnea (OSA) Excess fatty tissue in the throat can cover the airway during sleep, leading to repeated pauses in breathing and increasing the risk of OSA. And because a lack of sleep increases levels of the appetite-stimulating hormone ghrelin in the body, OSA can lead to even more weight gain.
  • Joint Health Overweight and obesity can also contribute to osteoarthritis, a painful joint condition, in two ways: Fat releases inflammatory chemicals that can cause pain and swelling, and excess weight puts added pressure on the joints.

Metabolic Health

Most people who are overweight or have obesity also exhibit signs of metabolic health issues, such as high blood pressure, high blood sugar, and high cholesterol, all of which increase the risk of chronic disease. Some people manage to avoid these health problems, which doctors sometimes refer to as “metabolically healthy obesity.”

“Metabolically healthy obesity refers to people who have a higher BMI but normal blood sugar, cholesterol, blood pressure, and no clear signs of inflammation or insulin resistance,” says Lopez-Jimenez. “This state is often temporary. Over time, many will develop metabolic abnormalities.”

Even if you’re considered metabolically healthy and feel fine, it’s still important to lose weight, because obesity is a progressive disease, says Lopez-Jimenez.

Current Management and Treatment Options

If you’re overweight or have obesity, work with your healthcare provider to determine how much weight would be healthy for you to lose as well as at what rate and with what interventions. Losing just 5 to 10 percent of your body weight can provide health benefits, including improvements in blood pressure and cholesterol levels.

Nutrition and Lifestyle Changes

Diet and exercise are the foundations of any weight loss plan. The best type of diet for weight loss is one that features plant-based foods like fruits, vegetables, and whole grains as well as lean protein sources like fish, skinless chicken breast, beans and lentils, and tofu. It’s also low in processed and ultra-processed foods and added sugar.

Activity guidelines also recommend aiming for a minimum of 150 minutes of moderate-intensity aerobic exercise, like walking or bike riding, each week, plus two days featuring muscle-strengthening workouts.

The New Era of Medications

If diet and exercise alone aren’t getting you to your weight loss goal, medication may be an option.

Most prescription weight loss medications work by helping you feel full with less food or by preventing your body from absorbing as much fat from food.

 To get a prescription for weight loss medication, you may need to be diagnosed with obesity or have a BMI of at least 27 plus a weight-related health condition, such as diabetes or high blood pressure.

Weight loss medications approved by the U.S. Food and Drug Administration (FDA) include:

  • diethylpropion (Tenuate)
  • liraglutide (Saxenda)
  • naltrexone/bupropion (Contrave)
  • orforglipron (Foundayo)
  • orlistat (Alli)
  • phendimetrazine (Bontril)
  • phentermine-topiramate (Qsymia)
  • semaglutide (Wegovy)
  • tirzepatide (Zepbound)
These drugs have helped people lose 3 to 18 percent more of their starting weight over one year compared with those navigating weight loss without medication assistance.

Some of the newer obesity drugs, known as glucagon-like peptide-1 (GLP-1) receptor agonists, can result in even more significant weight loss, especially when administered at higher doses. In two separate 72-week clinical trials, participants on the highest dose of tirzepatide and those taking a high dose of semaglutide lost about 21 percent of their starting weight.

Surgical and Procedural Options

Bariatric surgery, or weight loss surgery, is another option for people who are struggling to lose weight. During these procedures, a surgeon removes most of the stomach (gastric sleeve) or creates a smaller stomach pouch and attaches the small intestine to it (gastric bypass). The goal of these surgeries is to make the person feel full on a smaller amount of food.

These procedures can help an individual lose a lot of weight, but they do come with risks and aren’t for everyone. To qualify for weight loss surgery, you must meet one of the following criteria:

  • A BMI of 40 or higher
  • A BMI of 35 or higher and a serious weight-related health condition, like type 2 diabetes or heart disease
  • A BMI of 30 or higher and type 2 diabetes that’s difficult to control with other treatments

FAQ

What is the difference between being overweight and obese?
Overweight is defined as a BMI between 25 and 29.9. It’s often caused by an energy imbalance. Obesity is defined as a BMI of 30 or higher and is recognized as a chronic, multifactorial disease.
While being overweight carries fewer immediate health risks than obesity, it’s still associated with a higher likelihood of developing high blood pressure, heart disease, and type 2 diabetes. Experts recommend healthy weight management to prevent future chronic illness.
Physicians categorize obesity based on BMI severity: Class 1 is defined by a BMI of 30 to 34.9, class 2 is defined by a BMI of 35 to 39.9, and class 3 is defined by a BMI of 40 or higher.
While BMI remains the primary screening tool for obesity, doctors also consider waist circumference and visceral fat distribution as more critical indicators of one’s health risk.
The best treatment for obesity is a combination of personalized interventions managed by a healthcare provider. Treatment may include nutrition and lifestyle changes, prescription weight loss medication, or bariatric surgery.

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