- Excess belly fat is linked to a higher risk of early death, according to the largest study of its kind.
- Bigger hips and thighs were found to be associated with a lower risk of early death.
- Extra fat around the middle may be dangerous due to its effect on internal organs, and a larger lower body may be beneficial due to its link to improved metabolic and heart health.
- The study strengthens past work suggesting measurements of belly fat are better indicators of health than body mass index.
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The more fat you carry around your middle, the more likely you are to die early from any cause — even if you don’t have much body fat overall, according to the largest study of its kind published Wednesday in the journal BMJ.
In contrast, bigger hips and thighs are associated with a lower risk of early death, the meta-analysis also found.
These findings bolster past research suggesting that belly fat is particularly dangerous and a better indicator of health than weight or body mass index (a height-to-weight ratio).
Each four-inch increase in hip circumference was linked to an 11% higher risk of death from any cause
For the analysis, researchers from institutions in Iran and Canada reviewed 72 studies that included over 2.5 million participants around the world who were tracked between three and 24 years.
All the studies included reported at least three measures of central fatness, like waist circumference, waist-to-hip ratio, and a body shape metric. Many also included other body size metrics like hip and thigh circumference.
The researchers found that most measures of belly fat were associated with a higher risk of early death from any cause, called all-cause mortality. For example, each four-inch increase in waist circumference was linked to an 11% higher risk of all-cause mortality.
Larger hip and thigh circumferences, however, seemed to have a protective effect. For instance, each four-inch increase in hip circumference was associated with a 10% lower risk of all cause mortality, while each two-inch increase in thigh circumference was associated with an 18% lower risk.
“Hip fat is considered beneficial and thigh size is an indicator of the amount of muscle, which is protective,” Tauseef Ahmad Khan, a post-doctoral fellow in the University of Toronto’s Department of Nutritional Sciences and one of the study authors, told Insider.
Belly fat may be especially dangerous because of how it interferes with organs
The current study couldn’t weed out all underlying conditions that might explain the link between early death and central fatness.
But its results still strengthen past findings suggesting excess belly fat can be detrimental to health.
Earlier work has shown having a waist size higher than 40 inches around for men or 34.5 inches for women is correlated with a higher risk for developing type 2 diabetes and heart attack, Business Insider previously reported. Some evidence even suggests having more belly fat is correlated with lower cognitive performance.
Health professionals are still learning why fat around the middle may be tied to adverse health outcomes while more pear-shaped bodies seem to have health benefits.
One prevailing explanation is that fat inside the body, known as visceral fat, as opposed to subcutaneous fat, or the fat you can pinch, may interfere with the normal functioning of internal organs.
Bigger hips and thighs, meanwhile, seem to be associated with better markers or heart and metabolic health, the study authors write.
BMI is an imperfect indicator of health
The analysis also supports the notion that BMI, a height-to-weight ratio, is a faulty indicator of health since it doesn’t differentiate between muscle weight and fat weight, nor does it identify where on the body the fat is held.
For instance, a 5-foot-1-inch, 160-pound woman is considered obese, regardless of whether her fat accumulates around her waist and contributes to diabetes or she’s healthy but bigger around the hips and thighs.
That reality informed Canada’s clinical guidelines, which were updated in August to define obesity not as a ratio of height to weight, but as a chronic disease in which excess body fat impairs health.
Still, some health professionals say any metric that suggests certain bodies, rather than behaviors or societal influences, lead to health consequences isn’t helpful, and can perpetuate weight stigma — which is linked to negative health outcomes on its own.
“Why divide people by size at all?” registered dietitian Rebecca Scritchfield previously told Insider. “Thin people and fat people can have similar behavioral difficulties with mindful self-care and need a combination of psychological support and medical nutrition therapy.”
Many factors influence how much belly fat you have, like genetics, hormones, diet, and age. Men in particular tend to accumulate abdominal fat.
“While one cannot target where one loses fat from,” Khan said, “losing weight through diet and exercise will also reduce waist and therefore belly fat.”