Metabolically healthy obesity: a closer look
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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 considers height.
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.
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.”
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
According to the World Health Organization (WHO), a BMI between 18.5 and 24.9 is considered normal weight, a BMI between 25 and 29.9 is considered overweight, and a BMI over 30 is considered obese.
The Flaws of BMI
While BMI may seem like a straightforward and objective measure of health, it has several limitations that make it less reliable than we might think.
It Doesn't Take into Account Body Composition
One of the main flaws of BMI is that it doesn't take into account body composition. BMI only considers weight and height, which means that two people with the same BMI could have very different amounts of body fat and muscle mass. This is particularly problematic for athletes and bodybuilders, who may have a high BMI due to their muscle mass, but are actually very healthy.
It Ignores Where Fat is Located in the Body
Another limitation of BMI is that it doesn't take into account where fat is located in the body. Research has shown that fat located in certain areas of the body, such as the waist or abdomen, is more harmful to health than fat located in other areas. However, BMI doesn't differentiate between different types of fat, which means that two people with the same BMI could have very different levels of visceral fat (the type of fat located around the organs that's associated with a higher risk of disease).
It Doesn't Account for Ethnicity or Gender
BMI was originally developed by a Belgian mathematician named Adolphe Quetelet in the 1800s, and it was based on data from European men. However, research has shown that BMI may not be an accurate measure of health for people from different ethnic backgrounds or genders. For example, some studies have suggested that BMI thresholds for obesity should be lower for Asian populations, who are at a higher risk of developing obesity-related diseases at lower BMI levels.
It Doesn't Consider Lifestyle Factors
Finally, BMI doesn't take into account lifestyle factors that can affect health, such as diet, exercise, and stress levels. While BMI can give us a general idea of whether someone is in a healthy weight range, it doesn't provide any information about their overall health or the lifestyle factors that may be affecting their weight. For example, someone with a normal BMI may still be at risk for health problems if they have poor eating habits or don't exercise regularly.
The Need for a More Comprehensive Approach to Health
Given the limitations of BMI, it's clear that we need a more comprehensive approach to assessing health. This approach should take into account not just weight, but also other factors that affect health, such as body composition, lifestyle habits, and underlying medical conditions.
One alternative measure that's gaining popularity is waist circumference, which is a measure of the amount of fat around the waist. Research has shown that waist circumference may be a better predictor of health risks than BMI, particularly for people with a BMI in the overweight or obese range.
Another approach is to focus on overall health and well-being rather than just weight. This includes factors like blood pressure, cholesterol levels, and blood sugar levels, as well as lifestyle habits like exercise, diet, and stress management. By taking a more holistic approach to health, we can get a better picture of someone's overall health and well-being, and develop targeted interventions to improve their health.
While BMI has been a popular measure of weight and health for decades, it has its limitations. BMI only considers weight and height, and doesn't consider factors like body composition, where fat is located in the body, or lifestyle habits. As a result, it may not be a reliable indicator of health for everyone. To get a more comprehensive picture of someone's health, we need to look beyond BMI and consider other health measures, such as waist circumference and overall health and well-being. By doing so, we can develop more targeted interventions to help people improve their health and prevent chronic diseases.