Each 10% Increase In Body Fat Increases Mortality Risk By 11%

• Higher body fat (including percentage, fat mass, or visceral adipose tissue amount) is linked to higher risk of all-cause mortality, as found in a meta-analysis with almost 1 million participants. 

• For every 10% increment in body fat, risk for all-cause mortality increased by 11%. 

• In addition, risk for all-cause mortality increased by 6% for each 5 kg (11 lb) increment in fat mass and 17% for each 1 standard deviation increase in visceral adipose tissue.

• The relationship between body fat percentage or fat mass and risk of mortality was J-shaped, in that mortality also increases for those with too-low body fat. 

• The lowest risk for all-cause mortality was at a body fat percentage of 25% and a fat mass of 20 kg (44 lbs).

This news article was posted on Healio.com:

Higher body fat, whether determined by percentage, fat mass, fat mass index or visceral adipose tissue, was associated with higher risk for mortality among adults, according to study data.

“Accurate technology, such as CT and DXA, or alternative methods representing an indirect estimate of body fat content, such as bioelectrical impedance analysis or validated equations, can present more accurate estimation of body fat stores,” Ahmad Jayedi, MD, of the Social Determinants of Health Research Center at Semnan University of Medical Sciences and the department of community nutrition at the School of Nutritional Science and Dietetics at Tehran University of Medical Sciences in Iran, and colleagues wrote in International Journal of Obesity.

In this systematic review and dose-response meta-analysis, researchers searched PubMed, Scopus and Web of Science for prospective studies published through June 2021 about the relationship between body fat percentage and risk for all-cause mortality in the general population. Researchers identified 35 prospective cohort studies with 923,295 participants and 68,389 deaths.

For every 10% increment in body fat, risk for all-cause mortality increased by 11% (HR = 1.11; 95% CI, 1.02-1.2) in the general adult populations. In addition, risk for all-cause mortality increased by 6% for each 5 kg increment in fat mass (HR = 1.06; 95% CI, 1.01-1.12) and 11% for each 2 kg/m² increment in fat mass index (HR = 1.11; 95% CI, 1.06-1.16), and 17% for each 1 standard deviation increase in visceral adipose tissue.

Researchers observed a J-shaped association between body fat percentage and fat mass and risk for all-cause mortality. The lowest risk for all-cause mortality was at a body fat percentage of 25% and a fat mass of 20 kg. Researchers also observed little evidence of between-subgroup heterogeneity. Positive associations between fat and mortality were greater in studies with longer duration, those that excluded participants with prevalent cardiovascular disease and cancer at baseline and those that adjusted for smoking or included only never smokers in subgroup analyses.

These associations were less pronounced in studies that adjusted for potential mediating factors. This suggested an impact of reverse causation, confounding and overadjustment in some studies, the researchers wrote.

“Further studies with longer durations of follow-up and larger sample size are needed to clarify potential residual confounding by smoking and reverse causation,” they wrote.

Study Source: 

Jayedi, A., Khan, T.A., Aune, D. et al. Body fat and risk of all-cause mortality: a systematic review and dose-response meta-analysis of prospective cohort studies. Int J Obes 46, 1573–1581 (2022). https://doi.org/10.1038/s41366-022-01165-5