Overweight and obesity are body weight classifications based on the body mass index (BMI), a screening tool that divides an individual’s weight in kilograms by the square of their height in meters.
People with obesity weigh more for their height than those who are overweight and are at a higher risk of several health conditions, including type 2 diabetes and high blood pressure.
The BMI on its own is not a comprehensive representation of a person’s individual health, which is why it’s important to speak with a healthcare provider to get the right tests and lab work done to determine your health status.
Overweight and obesity are two classifications according to the body mass index (BMI). When using the BMI, there are four possible classifications: underweight, healthy weight, overweight, and obese. There are also three subcategories under obesity: class 1 obesity, class 2 obesity, and class 3 obesity.
People who fall into the obese category weigh more for their height than those who fall into the overweight, healthy weight and underweight categories. People with obesity are also at risk for several health conditions, including heart disease and type 2 diabetes. Class 3 obesity is also associated with a higher risk of economic and social disadvantages and a lower quality of life.
This article discusses the differences between overweight and obesity, how to calculate your BMI, and when to consult a medical professional about your health.
What is Overweight?
Overweight is a body weight classification defined by BMI. People who are overweight weigh more for their height than people who fall into the “healthy weight” and “underweight” BMI ranges, but less than people who fall into the “obese” BMI category.
Adults with a BMI between 25.0 to < 30 are considered overweight. According to data from 2017–2018, an estimated 30.7% of adults in the United States are considered overweight. The data also shows that the percentage of overweight adult males is slightly higher than the percentage of overweight adult females.
Unlike adults, children under the age of 18 are constantly growing, which can make it more difficult to track their BMI, as both their height and weight are meant to increase throughout puberty. The differences in their body composition also vary depending on their sex. For this reason, a child’s weight status is calculated based on a comparison with other children of the same sex in their age range. Overweight children are those whose weight falls into the 85th to less than 95th percentile.
What is Obesity?
Obesity is the highest body weight classification defined by BMI. People who are obese weigh more for their height than people who fall into the “overweight,” “healthy weight,” and “underweight” BMI ranges.
Adults with a BMI of 30.0 or higher are considered obese according to the BMI. Adults with a BMI between 30 to < 35 are considered class 1 obese, and adults with a BMI between 35 to < 40 are considered class 2 obese. Adults with a BMI of 40 or higher are considered class 3 obese (sometimes referred to as “severe” or “morbid” obesity.) According to the National Institute of Health, roughly 42.4% of adults in the United States have obesity. Also, obesity is slightly more prevalent in adult males than in adult females.
According to the National Institute of Health, roughly 19.3% of children in the U.S. aged 2–19 are considered obese.
Overweight vs Obese
Both overweight and obesity are examples of BMI classifications. People with obesity weigh more for their height than those who are overweight. Though neither classification directly measures body fat or body composition, people with obesity are more likely to be at risk for several health conditions, including heart disease, type 2 diabetes, high blood pressure, and more.
According to a study using data collected between 1992 and 2002, an overweight BMI classification was associated with fewer excess deaths than both the underweight and obese classifications.
In order to calculate your BMI, you must divide your weight in kilograms by the square of your height in meters. However, it’s important to note that BMI is not a reliable indicator of individual health, nor does it measure your body fat or body composition. Instead, the BMI can be used as one of many possible tools (including blood tests, urine samples, image scans, and more) that can be used to get a more complete and comprehensive picture of one’s health.
What Causes Overweight and Obesity?
There are many factors that can contribute to a person’s weight. But the majority of research has found that weight, and, in particular, obesity, is mainly genetic. This means that a person’s body size is highly dependent on their family history of being overweight or obese.
Other factors that can affect weight include:
- Level of physical activity or exercise
- Dietary patterns
- Sleep habits
- Medical conditions, including endocrine disorders
- Living in a food desert
- Decreased energy metabolism
Health Risks of Overweight and Obesity
Having overweight or obesity can increase your risk of certain physical and mental health conditions and your experience of various stigmas. In most cases, obesity is more strongly associated with these increased risks.
Some of the health risks associated with being overweight and obese include:
- Type 2 diabetes
- High blood pressure, or hypertension
- Heart disease
- Sleep apnea
- Metabolic syndrome
- Fatty liver diseases
- Gallbladder diseases
- Certain types of cancer
- Kidney disease
- Pregnancy complications
- Weight bias and stigma, including from healthcare providers
Seeking Medical Attention for Overweight and Obesity
Though calculating your BMI is easy to do and only requires two pieces of data—your height and your weight—it should not be used on its own to determine your health status. To get a more personalized picture of your health, it’s important to reach out to a medical professional. They can help you get access to the right tests and screens that will give you a more comprehensive diagnosis of your health status.
If your healthcare provider recommends weight loss treatment or a variety of treatments that include weight loss, be sure to ask them about strategies that can help you lose weight safely and sustainably. In many cases, losing just 5–10% of your body weight can improve your overall health and metabolic factors.
Additional treatment strategies your healthcare provider may recommend include:
- Nutrition: Following a healthy and balanced eating pattern can benefit your physical health in the long term.
- Getting regular exercise: Experts recommend at least 150-300 minutes of moderate-intensity exercise per week or 75-150 of vigorous-intensity aerobic exercise per week.
- Behavioral therapy: This approach can be especially helpful for those with a history of disordered eating, which research shows contributes to an estimated 50% of severe obesity cases.
- Prescription medications: Several medications can help to support weight loss in people with overweight and obesity. Examples of medicines used to treat obesity include semaglutide (Wegovy), liraglutide (Saxenda), orlistat (Xenical), phentermine-topiramate (Qsymia), naltrexone-bupropion (Contrave), and setmelanotide (IMCIVREE).
- Surgery: In some cases, a medical professional may recommend weight-loss surgery. However, these solutions are irreversible and carry serious risks, including infection, postoperative bleeding, malabsorption, vitamin and mineral deficiency, cardiac events, and more.
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Frequently Asked Questions
K Health articles are all written and reviewed by MDs, PhDs, NPs, or PharmDs and are for informational purposes only. This information does not constitute and should not be relied on for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment.
K Health has strict sourcing guidelines and relies on peer-reviewed studies, academic research institutions, and medical associations. We avoid using tertiary references.
Behavioral Approaches to Obesity Treatment. (2022).
Defining Adult Overweight & Obesity. (2022).
Excess Deaths Associated with Underweight, Overweight, and Obesity. (2005).
Facing Morbid Obesity: How to Approach It. (2015).
Health Risks of Overweight & Obesity. (2018).
Obesity: Lifestyle Modification and Behavior Interventions. (2020).
Overweight & Obesity Statistics. (2021).