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Overweight and healthy: the concept of metabolically healthy obesity

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Metabolically healthy obesity: a closer look

Harvard Health Publishing provides access to its archived content to help its readers. It is important to note the date each article was posted or last reviewed. No content on this site should be used as a substitute for medical advice from a qualified clinician.

Being overweight or obese is often linked to health problems, but not everyone who falls into these categories is affected in the same way. Some individuals manage to escape the usual hazards, at least for a while, and are said to have “metabolically healthy obesity.”

According to health professionals, being overweight is defined as having a body-mass index (BMI) between 25.0 and 29.9, while obesity is a BMI of 30 or higher. BMI is a measure of weight that takes height into consideration.

However, most overweight or obese people exhibit potentially unhealthy changes in metabolism, including high blood pressure, high cholesterol, and insulin resistance. These changes can damage arteries in the heart and other parts of the body, increasing the risk of a heart attack, stroke, or type 2 diabetes.  Research suggests that people with metabolically healthy obesity have a higher risk of developing metabolic abnormalities than people who do not have obesity.

Despite this, some overweight or obese people manage to avoid such changes and appear metabolically healthy. “Obesity isn’t a homogeneous condition,” says Dr. Frank Hu, a professor of nutrition and epidemiology at the Harvard School of Public Health. “It appears that it doesn’t affect everyone in the same ways.”

The heterogeneity in the metabolic complications associated with obesity has important clinical implications, particularly in the current era of precision medicine and cost-effectiveness.

In a “Personal View” article published in Lancet Diabetes and Endocrinology, Dr. Hu and three colleagues reviewed what is currently known about metabolically healthy obesity. They identified several characteristics of this condition, including a high BMI, but with a waist size of no more than 40 inches for men or 35 inches for women, normal blood pressure, cholesterol, and blood sugar, normal insulin sensitivity, and good physical fitness.

The Limitations of BMI as a Measure of Weight and Health

Body: Body mass index (BMI) is a widely used tool to assess weight and health status. However, it is not a perfect measure, as it can classify fit, muscular individuals as overweight or obese due to the density of muscle tissue. In contrast, fat tissue converts blood sugar into fat and stores it, which can be harmful.

Dr. Hu suggests that exploring metabolically healthy obesity could help refine our understanding of the implications of obesity. BMI should not be the sole factor for assessing health, as genetics also play a role in how a person's body and metabolism respond to weight. Some individuals may be genetically protected from developing insulin resistance, while others may store fat in different areas of the body, which can affect metabolic health. It has been proposed that metabolically healthy obese individuals might be protected against obesity-related diseases. The extent of this protection has been controversial within the scientific community, and this is partly because we still don't have a standardized definition of MHO. 

The concept of metabolically healthy obesity could guide treatment options for individuals struggling with their weight. While exercise and a healthy diet are the foundation for treating obesity, weight-loss surgery may be appropriate for those with metabolically unhealthy obesity. However, for people with metabolically healthy obesity, intensifying the lifestyle approach may be a better option than surgery. This idea needs to be tested in clinical studies to determine its efficacy.

Metabolically Healthy Obesity: What You Need to Know


While metabolically healthy obesity may exist, it is not common, and it may not be permanent. Dr. Hu warns that a person's metabolic health can change over time due to aging, a decrease in exercise, or other lifestyle changes. Therefore, individuals should not become complacent even if they have metabolically healthy obesity at one point. Science has proven that chronic, low-grade inflammation can turn into a silent killer that contributes to cardiovascular disease, cancer, type 2 diabetes, and other conditions.

It is also important to keep in mind that obesity can cause more harm than just metabolic issues. Excess weight can damage joints, lead to sleep apnea and respiratory problems, and increase the risk of developing several cancers. Thus, even if a person has metabolically healthy obesity, it is not a desirable or sustainable condition.

In Conclusion,

While BMI is a useful tool to assess weight and health status, it has limitations. The concept of metabolically healthy obesity may help guide treatment options, but it is not a permanent state, and other factors beyond metabolic health must be considered. Regardless of metabolic health status, excess weight can harm the body, so it is important to prioritize a healthy lifestyle to maintain overall health and well-being.

Caroline Buckee

Caroline Flannigan is an epidemiologist. She is an Associate Professor of Epidemiology and is the Associate Director of the Center for Communicable Disease Dynamics.

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