In discussions about weight, the terms “overweight” and “obesity” often come up. But what exactly do these terms mean, and how are they different? This article breaks down these concepts to help you better understand the difference between overweight and obesity, along with what these conditions might mean for your health.

The Limits of BMI in Assessing Health

Body mass index (BMI) is a number used to group people based on weight and height. BMI is calculated by dividing a person’s weight in kilograms by their height in meters squared. BMI categories differ by age and are meant to estimate body fat.

According to the World Health Organization (WHO), a BMI of 25 to 29.9 is considered overweight, and a BMI of 30 or higher is considered obesity.

However, using BMI has some major limits and doesn’t tell the full story about a person’s health. For example:

• BMI can be inaccurate, sometimes mistakenly showing someone as overweight or obese or missing excess body fat.
• It doesn’t distinguish between fat and muscle or where fat is stored in the body.
• Two people with the same BMI can have very different body compositions and health risks. For example, a muscular athlete might have a high BMI but low body fat, while someone else with the same BMI might have less muscle and more fat, putting them at higher risk of health problems.
• BMI may not work the same way for all racial or ethnic groups. For example, people of Asian descent are more likely to store fat around the belly, which raises heart disease risk.

A New Understanding of Obesity

Researchers and doctors now say BMI should be used to spot health risks and trends in large groups of people, such as in research or health screenings, not for judging one person’s health. Healthcare providers today also use new, more accurate terms to describe obesity — “preclinical obesity” and “clinical obesity.”

Preclinical obesity means a person has excess body fat, but their organs (like the heart or kidneys) are still working normally. Preclinical obesity can raise the risk of later health problems, but it isn’t considered a disease.

Clinical obesity means that extra body fat is already harming the body. It can damage tissues and organs or make everyday activities, like walking or getting dressed, much harder. People with clinical obesity often have related health conditions, such as heart, lung, or kidney issues.

‘Preclinical Obesity’ Isn’t the Same as ‘Overweight’

“Overweight” usually means having a BMI between 25 and 29.9, but preclinical obesity is diagnosed through tests that show a person has too much body fat, even if their organs still work fine. Because BMI isn’t always accurate, some people who are called overweight might actually have preclinical obesity or even clinical obesity.

Other Ways To Measure Body Fat

Fat stored around the belly (called visceral fat, which causes an apple-shaped body) is more harmful than fat in the hips and thighs (subcutaneous fat, which causes a pear shape). That’s why other ways to measure body fat may be more useful than BMI. These methods can show more clearly whether a person has too much body fat and where it’s located. Healthcare providers might use:

• Direct body fat tests, like dual-energy X-ray absorptiometry (DEXA scan) or bioelectrical impedance, which use harmless electrical signals to estimate fat levels
• Body measurements, such as waist size, waist-to-hip ratio, or waist-to-height ratio, which are then compared to healthy ranges based on age, gender, and race or ethnicity

These tools give doctors a much better picture of someone’s health than BMI alone.

Health Implications of Extra Body Fat

Being overweight or having obesity can raise your risk of several health problems. For example, excess fat around the waist is linked to a higher chance of developing metabolic syndrome — a group of conditions including type 2 diabetes, heart disease, and stroke. Other health risks include:

• Hypertension (high blood pressure)
• Certain types of cancer
• Breathing problems, such as asthma and sleep apnea (when breathing stops and starts during sleep)
• Joint pain and damage, like osteoarthritis and gout
• Fatty liver diseases, which can lead to liver damage or failure
• Mental health conditions or mood disorders, like anxiety and depression

Causes of Overweight and Obesity

Weight gain is influenced by more than just what you eat or how much you move. A mix of factors — including genetics, environment, habits, medical conditions, and even medications — can affect your weight.

Genetics

Your genes can play a significant role in metabolism — how your body processes and stores fat. Scientists believe that at least 15 genes can affect a person’s risk of gaining weight and developing obesity. However, having a higher genetic risk doesn’t mean that weight gain is guaranteed. Other factors, such as lifestyle choices, still have a big impact.

Environment

Your surroundings can greatly affect your weight. Studies have shown that walkable areas with green spaces and sidewalks may encourage people to be more active.

Access to healthy food is important too. Living near a grocery store or farmers market may make it easy to plan nutritious meals, while having lots of fast-food restaurants nearby can make it harder to make healthy choices. Your food choices might also be influenced by income.

Lifestyle Factors

Everyday choices play a big role in weight. Lifestyle factors that can make a difference include:

• Eating patterns — Taking in more calories than your body uses, especially from sugary or fatty foods, can lead to weight gain. Choosing healthier foods, such as whole grains, fruits, and vegetables, can help you maintain a healthy weight.
• Physical activity — A sedentary lifestyle can increase your BMI. Healthcare specialists recommend that most adults aim for 150 minutes of exercise a week.
• Sleep — Poor sleep can disrupt hormones that control hunger and fullness, making it harder to avoid overeating.
• Stress — When you’re stressed, your body releases hormones like cortisol that increase appetite and make your body store more fat.
• Screen time — Spending lots of time in front of a computer or TV, which may indicate a lack of physical activity, has been linked to a higher BMI.

Medical Conditions

Unexpected weight gain could signal an underlying condition such as:

• Type 2 diabetes (persistently high blood sugar)
• Sleep apnea
• Some kidney diseases
• Thyroid problems, such as hypothyroidism
• Cushing’s syndrome (high cortisol levels)

Medications

Many commonly prescribed medications can interfere with the body’s chemical signals and cause weight gain as a side effect. These drugs include:

• Antipsychotics
• Antidepressants
• Diabetes drugs like insulin or sulfonylureas
• Beta-blockers (used for high blood pressure)
• Glucocorticoids (for autoimmune conditions)
• Hormonal birth control

Don’t stop taking medication without your doctor’s guidance. If you’re concerned about weight gain, talk to your healthcare provider. There may be alternative treatments that work better for your needs.

A Personalized Approach to Health

Weight is just one aspect of your overall health. Two people with the same BMI can have very different health profiles. Someone labeled “overweight” may have healthy blood pressure, cholesterol, and blood sugar, whereas someone in the “normal” BMI weight range might have health problems linked to metabolism or heart health. This is why many healthcare providers are shifting toward a more personalized approach — looking at your full health picture, not just a number on a scale.

Talking With Your Healthcare Provider

If you’re concerned about your health, it’s important to focus on your personal situation. Here’s how to approach a conversation with your doctor:

• Talk about your individual risk factors, including family history, your daily routine, and any symptoms or concerns.
• Set goals around health, not just weight, like improving nutrition, sleep, activity levels, and stress management.
• Be honest about your challenges, such as diets or treatments that haven’t worked for you.
• Ask about all your options — including lifestyle changes, medications, and surgery — to find out what’s right for you.

Health isn’t one-size-fits-all. A multidisciplinary care team — including doctors, dietitians, endocrinologists (specialists in conditions related to hormones), and mental health professionals — can help you better understand your body and find a plan that fits your needs.

Remember, you’re not alone. Support from healthcare professionals, family, and friends can help you feel more confident and in control of your health.

Talk With Others Who Understand

MyObesityTeam is the social network for people with obesity and their loved ones. On MyObesityTeam, more than 57,000 members come together to ask questions, give advice, and share their stories with others who understand life with obesity.

Have you been diagnosed with either overweight or obesity? Has your doctor talked with you about other factors that influence your health? Share your comments below, start a conversation by posting on your Activities page, or connect with like-minded members in Groups.