Low BMI, High Body Fat Linked to Mortality Risk

Low body mass index (BMI) and high body fat percentage are linked to increased all-cause mortality in patients aged 40 years and older, according to a new study.

Previous research found that elevated BMI scores may decrease mortality rates, but results were limited because not all measures were taken into consideration.
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To investigate the relationship between BMI and body fat percentage, researchers observed 54,420 patients aged 40 years and older who were referred for bone mineral density testing.

Patients were separated into 5 groups based on their body fat percentage: Group 1 had the lowest percentage, group 5 had the highest percentage, and group 3 was the reference. Body fat percentage was calculated via dual-energy x-ray absorptiometry (DXA).

Researchers included 49,476 women in the study whose mean age was 64 years, mean BMI was 27 kg/m², and mean body fat percentage was 32%. In addition, there were 4944 men involved in the study, with a mean age of 66 years, mean BMI of 27.4 kg/m², and mean body fat percentage of 30%.

After a median 6.7 years, nearly 10% of the women had died, and after a median 4.5 years, 20% of the men had died. A low BMI and high body fat percentage were linked to higher mortality rates in both women and men.

“Low BMI and high body fat percentage are independently associated with increased mortality,” researchers concluded. “These findings may help explain the counterintuitive relationship between BMI and mortality.”

—Amanda Balbi

Reference:

Padwal R, Leslie WD, Lix LM, Majumdar SR. Relationship among body fat percentage, body mass index, and all-cause mortality: A cohort study. Ann Intern Med. Published online March 8, 2016. doi:10.7326/M15-1181.