Why Being Skinny Fat Could Be Just as Dangerous as Being Obese

Everyone knows obesity carries the risk of a worrying number of diseases, from heart disease to type 2 diabetes. But a slim physique doesn't offer a free pass from chronic conditions, and growing evidence suggests being so-called skinny fat could be just as damaging as being obese.

The misconception that those who are slender are less likely to suffer from potentially life-threatening illnesses partly lies in how society often values thinness above health, and confusion over how the physiologically ideal body type is measured, experts told Newsweek.

Unlike obesity, which is identified as a body mass index (BMI) of 30 or more and excessive fat accumulation, "skinny fat" is a looser term.

"Skinny fat refers to people who fall into the normal category of weight for their height, a term called Body Mass Index, yet have a disproportionately high proportion of body fat," Dr. Eva Tseng, assistant professor medicine at the Johns Hopkins University School of Medicine, told Newsweek.

The "skinny fat" physique can lull its holders into a false sense of security when it comes to health. Getty Images

Professor Jimmy Bell, an expert in obesity and metabolism at the University of Westminster, U.K., puts it another way. Referring to the Oscar Wilde novel about a man who appears ageless but whose sins are marked by a painting unseen by the rest of the world, he dubbed it "Dorian Gray syndrome." Skinny fat is also known as normal weight obesity and TOFI: thin on the outside, fat on the inside.

What is clear, however, is that the potential health risks are very real indeed. Earlier this month, the authors of a study published in the journal Clinical Interventions in Aging warned the combination of low muscle mass and high body fat, or sarcopenic obesity, poses a double threat to brain health. Being skinny fat was linked to a decline in working memory, mental flexibility, orientation and self-control—symptoms seen in those with Alzheimer's disease.

Mounting evidence suggests the distribution of fat and dense muscle mass are in fact more important than an individual's total fat levels, according to Bell. By wrapping around vital organs like the heart, liver and pancreas, visceral ectopic fat is believed to contribute to the development of type 2 diabetes, cancer and coronary heart disease, said Bell. Reduced skeletal muscle mass, meanwhile, is linked with poor mental cognition.

And those who carry their weight around the abdomen have a higher risk of premature cardiovascular disease, diabetes and death compared to people with a similar BMI but less abdominal adiposity, said Dr. Neil Thomas, professor at the Institute of Applied Health Research at the University of Birmingham.

"It [being skinny fat] is likely caused by our modern way of life, sitting at a desk too much and eating too many calorie-dense, salty foods and drinking too much alcohol," he said.

The less widely recognized dangers of the skinny fat body type highlight the flaws of relying solely on the BMI scale to measure physiological health, the experts agreed. As there is no simple, direct way of measuring body fat, BMI is a useful way to calculate the health of general populations, and that is why BMI is used as a surrogate marker, despite its limitations, said Tseng.

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But it is less accurate when used on an individual basis. "It does not directly measure excess body fat and it does not adjust for factors like age, sex, ethnicity and muscle mass. It also does not tell us the distribution of body fat in a person," she said.

A lean, muscular bodybuilder might have a healthy body but score as obese on the BMI scale. Older people tend to have more body fat than younger people, although they have the same BMI. The same goes for women and men with the same score, and individuals of South and East Asian origin when compared with Caucasians, said Thomas.

At the same time, people who are obese may have "metabolically healthy obesity and may have a lower risk of developing those diseases compared to people with normal weight obesity," said Tseng. "Evidence about normal weight obesity and metabolically healthy obesity continue to evolve."

As our understanding of this body type develops, how can we determine if they fall into the skinny fat category. And, more, importantly, how can they prevent or reverse it?

An MRI body scan is the most revealing method, said Bell. But that's expensive, and it's unlikely a health care provider would offer such as service unless a person is sick.

Waist circumference is a cheaper and nearly as effective indicator, said Thomas: particularly if a person's measurements are larger than when they were 18 years old.

Perhaps unsurprisingly, maintaining constant vigilance of our diet and exercising as much as possible are the most important tools to gradually chip away at visceral, ectopic fat. Yo-yo diets, which Bell said are associated with a skinny fat body, should be avoided.

"The best advice for all people, regardless of whether they are normal weight or not, is to exercise regularly and eat healthy to prevent the development of excess body fat," said Tseng. The American Heart Association recommends at least 30 minutes of moderate-intensity aerobic activity at least five days per week for all adults.

Keeping our bodies on their toes, so to speak, is another trick for tackling not only the physical but the potential mental effects of a skinny fat body, such as dementia, said Bell. Scientists believe frequent bursts of intense exercise are more beneficial than sporadic physical activity. Go to the gym for three short sessions a week rather than once a week for two hours, he said.

"Move in as many ways as possible," he said. "Dance, skate, play sports. Because then you use your brain rather than sitting on a bike in the gym. Walk up the stairs instead of getting the lift. Walk to work if you can. Park far away [from your destination] and walk."

The take-home message? "People think that beauty is more important than health," said Bell. "It's not until you're 60s and 70s you realize beauty isn't important. The most important thing is health."