Many people believe that if they have a normal body mass index, or BMI, they are safe from health problems linked to being overweight.
But a new global study reveals that this assumption may not be true. Researchers found that more than 20% of adults with a normal BMI still have dangerous levels of abdominal fat that raise their risk of serious diseases such as high blood pressure, diabetes, and high cholesterol.
BMI has long been used as a quick way to estimate if someone is underweight, normal, overweight, or obese. However, BMI only considers weight and height—it does not show where fat is stored in the body.
This can be misleading because fat that builds up around the belly, known as abdominal or visceral fat, is more harmful than fat in other parts of the body. Even if a person’s weight is considered normal, having too much belly fat can silently damage their health.
Abdominal fat increases the risk of several health problems by triggering inflammation and disrupting how the body processes sugar and fat. It can cause insulin resistance, which leads to diabetes, and also increase triglyceride and cholesterol levels. Over time, these issues can develop into heart disease—the world’s leading cause of death.
The new study, published in *JAMA Network Open*, examined health data from 471,228 people aged 15 to 69 across 91 countries, collected between 2000 and 2020. The data came from the World Health Organization’s global surveys on chronic disease risk factors.
Researchers defined abdominal obesity as a waist measurement of at least 80 centimeters for women and 94 centimeters for men. Participants who had a normal BMI (between 18.5 and 24.9) but a large waist were classified as having “normal-weight abdominal obesity.”
The results were striking. Worldwide, about 21.7% of adults with a normal BMI had abdominal obesity. The rates varied by region—from about 15% in the Western Pacific to more than 32% in the Eastern Mediterranean. Lebanon had the highest rate at nearly 60%, while Mozambique had the lowest at about 7%.
People with normal BMI but large waistlines were far more likely to suffer from metabolic problems. Compared with those who had both normal BMI and normal waist size, they were 29% more likely to have high blood pressure, 81% more likely to have diabetes, 39% more likely to have high cholesterol, and 56% more likely to have high triglycerides.
These risks remained significant even after adjusting for factors like age, gender, and lifestyle habits.
The study also found some interesting patterns in lifestyle and education. Those with abdominal obesity were more likely to eat fewer fruits and vegetables and to be less physically active. Surprisingly, people with higher education levels were also more likely to have abdominal obesity, except in Africa, where education seemed to protect against it.
These findings suggest that health professionals and the public should not rely on BMI alone to assess health risks. A person can have a normal BMI but still be at high risk for serious conditions if they carry excess belly fat. Measuring waist circumference may provide a more accurate picture of a person’s overall health.
When the researchers analyzed regional differences, they found a few exceptions. For example, in the Americas, high cholesterol was not linked to abdominal obesity, and in Europe, high triglycerides were not significantly higher among those with belly fat.
However, the overall global pattern was clear—abdominal obesity is dangerous, even in people who appear to be of healthy weight.
In reviewing these results, it’s clear that focusing only on body weight can cause people to miss early signs of disease risk. This study reinforces the need for doctors to measure waist size as part of routine checkups and for individuals to pay attention to where they store fat, not just how much they weigh. Waist size can be a strong warning signal for hidden health risks.
In conclusion, this research highlights an important message: having a normal BMI doesn’t always mean you’re healthy. People with excess belly fat may be at higher risk of heart disease, diabetes, and other metabolic problems—even if the scale says their weight is normal.
Future health guidelines may need to include waist measurements as a standard screening tool to better identify at-risk individuals and prevent disease earlier.
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The study is published in JAMA Network Open.
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