‘Fat but fit’ is not a real thing, obesity study explains

MUNICH, Germany — The myth of being “fat but fit” is, again, being debunked by a new study. Researchers found that obese individuals, even if they appear healthy, have an increased risk of diabetes and heart disease.

In an in-depth study by German researchers, the phenomenon of metabolically healthy obesity (MHO), often referred to as “fat but fit,” was closely examined. The results reveal that even those obese individuals who seem health-wise favorable are still 50 percent more susceptible to coronary heart disease.

“Some 15-20% of people living with obesity have none of the metabolic complications we associate with the condition, namely abnormal blood sugar control and blood fats, high blood pressure, Type 2 diabetes, and other signs of cardiovascular disease,” says Professor Matthias Blüher from the University of Leipzig and the Helmholtz Center in Munich in a media release.

Surprisingly, statistics show that obese women have a higher likelihood of developing MHO, ranging between seven and 28 percent, as opposed to men, where MHO sits between two and 19 percent. Half of all obese individuals are also estimated to have at least two weight-induced complications.

The researchers emphasize that the behavior of adipose tissue in those with obesity, rather than solely measuring BMI, should be a determining factor for MHO classification. People with normally sized fat-storing cells, adipocytes, tend to exhibit fewer obesity complications. In contrast, those with enlarged and inflamed adipocytes are prone to conditions like insulin resistance, leading to metabolic issues. Additionally, the way that we store fat is likely key to whether or not obesity can be described as MHO.

“When people with obesity have fat stored viscerally, or internally around their organs (such as in the liver), the data show that these people are much more likely to develop Type 2 diabetes than those who store fat more evenly around their body,” Dr. Blüher notes.

Overweight or obese man exercising
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Furthermore, dysfunctional adipose tissue can result in tissue damage, fibrosis, and the release of harmful molecules contributing to end-organ damage. For instance, the fat-secreted hormones, adipokines, might directly affect vascular system cells, leading to atherosclerosis.

Addressing the core question of whether those categorized as MHO are genuinely healthy, Dr. Blüher’s team firmly debunked this widely accepted theory. The study author points out that even when compared to individuals of standard weight without associated health conditions, those with obesity but without such conditions still had a 50-percent elevated risk of coronary heart disease.

Historically, MHO individuals were a lower priority for obesity treatments due to their seemingly positive health status. Still, the team stresses the importance of treatment and weight loss recommendations for those with MHO.

“So there is still a residual increased risk for those people living with obesity, even with what we would call metabolically healthy obesity” Blüher elaborates. “Even in the absence of other cardiometabolic risk factors, increased fat mass and adipose tissue dysfunction contribute to a higher risk of Type 2 diabetes and cardiovascular disease. Therefore, weight management and recommendations for weight loss are still important for people living with metabolically healthy obesity.”

The study is published in the journal Diabetologia and was presented at the Annual Meeting of The European Association for the Study of Diabetes (EASD 2023).

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South West News Service writer James Gamble contributed to this report.

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