Gaining weight around your mid-section may be the makings of much more than a wardrobe crisis: It may also signal the start of a serious health crisis.
So warns a team of Canadian and Iranian researchers who conducted an extensive review of 72 studies involving more than 2.5 million patients from all over the globe.
"We found that excess fat in the abdomen -- called central fatness or belly fat -- is associated with a higher risk of death than overall body fat," said study author Tauseef Ahmad Khan. He is a postdoctoral fellow in the department of nutritional sciences at the University of Toronto's Faculty of Medicine.
That means that even if other areas of the body are in good shape, once fat starts to accumulate in the belly region, the risk of dying an early death goes up, Khan noted. So "people should be more concerned about their waist, rather than just focusing on [overall] weight or body mass index," he said.
Khan and his colleagues pointed out that body mass index, or BMI, has long been considered the gold standard for assessing an individual's weight status.
The problem: BMI is not precise. For one, it doesn't specify exactly where any excess fat is located on the body. Nor does it make a distinction between muscle and fat.
So the team set out to examine the results of previous investigations that looked for links between excess central fat and an elevated risk of dying due to any cause.
The studies had been conducted between 1999 and 2019 by researchers in the United States, Canada, Europe, Australia, Brazil, India, Indonesia, Japan, China, Korea, Iran and Tobago. All involved adults aged 18 and older, with patients tracked for from three to 24 years.
Previous studies, said Khan, "were limited to older people or just people living in the West. Our study, the largest to date, confirms these results in people living across the world."
The reviewed studies included a minimum of three different measures for assessing body fat. Some considered waist, hip and/or thigh circumference, while others tallied each individual's waist-to-hip/height or thigh ratios. In some cases, a body fat index was also included. Others honed in on the "body shape index," a unified measure of body height, mass and waist circumference.
By almost any measure, the team concluded that excess belly fat was directly associated with a higher risk for early death.
The investigators found that for every four inches or so of additional waist circumference, early death risk rose by 11%.
At the same time, however, Khan said, "our study also shows that hip size and thigh size was linked to lower risk of death." Specifically, every 2-inch increase in thigh circumference was linked to an 18% drop in early death risk.
Why? Because "thigh size is an indicator of the amount of muscle" a person carries, not fat, said Khan.
By contrast, "belly fat is the fat that is stored around the organs in the abdomen and its excess is linked to high cholesterol, high blood pressure, heart disease, diabetes and stroke. Therefore, having more belly fat can increase the risk of dying from these diseases," he added.
So when the fancy dress or tux no longer fits, what should you do? Lose weight, he advised.
"While one cannot target where one loses fat from, losing weight through diet and exercise will also reduce belly fat," Khan said.
Lona Sandon is program director in the department of clinical nutrition with the school of health professions at the University of Texas Southwestern Medical Center at Dallas. "If you want to lose belly [visceral] fat, step one is to get on a treadmill, bike, elliptical or strap on the rollerblades. Whatever your preference, work up a good sweat," she said.
"Aerobic exercise helps to decrease this type of fat. Add some resistance training in there, too. Do this as many days of the week you can. Five days would be great," Sandon suggested.
"Second step, cut out the extra calories in general," she said. "Start with the added sugar and fats, and replace with fruits and vegetables. Cut back on portion sizes. Also cut out excess alcohol."
And making the effort is definitely a good idea given that "the fat that builds up in the belly produces inflammatory compounds that increase risk for insulin resistance, type 2 diabetes and heart disease," she added.
"So, yes, the short answer is health professionals should consider waist circumference and use it as an indicator of belly fat, and progress toward goals of reducing belly fat," Sandon said.
Khan and his colleagues published their findings online Sept. 24 in the BMJ.
There's more on belly fat risk at Johns Hopkins Medicine.