Researchers have found that excess fat stored around the abdomen is associated with a higher risk of early death from any cause, regardless of overall body fat, whereas larger hips and thighs are associated with a lower risk.
The results, published in the journal The BMJ, suggest that measuring central fatness may be a more reliable indicator of risk of death from excess weight, and could be used alongside body mass index to help determine the risk of premature death.
Body mass index (BMI) is a simple measure widely used to assess people’s weight. But its reliability is often criticised, as it does not distinguish fat from muscle and does not tell us where body fat is stored.
“It is already well known that being overweight or obese is linked to a greater risk of heart disease, certain cancers, kidney disease, and neurological disorders,” said study authors from Semnan University of Medical Sciences in Iran.
Evidence also suggests that central fatness might be more strongly associated with risk of death than overall obesity, but previous data are inconclusive.
To explore this further, the research team set out to examine whether measures of central fatness are associated with the risk of all-cause mortality in the general population.
Their findings are based on the results of 72 studies involving over 2.5 million participants who were tracked for between three and 24 years. All of the studies reported risk estimates for at least three measures of central fatness.
This included waist circumference, hip circumference, thigh circumference, waist-to-hip ratio, waist-to-height ratio, waist-to-thigh ratio, body adiposity index (a measure of total body mass made only of fat tissue), and a body shape index.
The researchers found that most measures of abdominal adiposity including waist circumference, waist-to-hip ratio, waist-to-height ratio, waist-to-thigh ratio, and body shape index were significantly and positively associated with higher all-cause mortality risk.
For example, each 10 cm (3.94 inches) increase in waist circumference was associated with an 11 per cent higher risk of all-cause mortality.
In contrast, larger hip and thigh circumference were associated with a lower risk of all-cause mortality.
The researchers noted that these associations remained significant after accounting for body mass index, suggesting that abdominal deposition of fat, independent of overall obesity, is associated with a higher risk.