Older adults with adequate or high muscle power are at lower risk of all-cause mortality risk. However, being obese offset this beneficial effect of muscle power, suggests a study published in the British Journal of Sports Medicine.¹

This study involved 2563 non-institutionalized Spanish older adults, aged 65‒91 years, from the EXERNET multicentre study to examine the association between muscle power and adiposity and all-cause mortality risk. The fat but powerful (F+P) (or fat but fit) paradox in this age group was also looked at. At the start of the study, the researchers measured the body mass index (BMI), waist circumference, body fat percentage (BF%) and fat index. Relevant demographic and medical data was collected. They underwent the sit-to-stand muscle power test (allometric and relative power). The study subjects were segregated into four groups: lean and powerful (L+P), F+P, lean but weak and fat and weak (F+W). Data were collected from June 2008 to November 2009.

During the follow-up of 8.9 years (median), participants who were fat but powerful (F+P) and lean and powerful (L+P) had the most survival benefit compared to the other groups when BMI and waist circumference were considered; HR 0.55 and 0.63 vs HR 0.57 and 0.58, respectively.

When the body fat percentage was considered, reduction in all-cause mortality was noted in the L+P group (HR 0.53), while a declining trend was observed in the F+P group (HR 0.57). But when the association between fat index and all-cause mortality was examined, only the lean and powerful group was found to benefit (HR 0.50). Older adults with higher levels of relative muscle power lowered their all-cause mortality risk (HR 0.63 and 0.53) after nearly 9 years of the study.

Results of this study point out that older adults with adequate muscle power showed better survival compared to those with low muscle power regardless of BMI, waist circumference and body fat percentage. But this survival benefit was neutralized among obese participants (as per fat index). Use of BMI, waist circumference and body fat percentage, but not fat index, established the fat but powerful paradox.

Obese individuals whose cardiorespiratory fitness is satisfactory are at low risk of mortality compared to non-obese persons with low cardiorespiratory fitness. This is the “fat but powerful or fit” paradox. However, when evaluating physical fitness among older adults, muscle power has greater correlation with functional status vis a vis their cardiorespiratory status.

These findings indicate that low muscle power is an independent risk factor for all-cause mortality. Evaluation of relative muscle power should be integrated in day to day clinical practice. And, when assessing for obesity, fat index should be the “preferred” marker as it “better and more independently reflects the amount of fat mass an individual has”, write the authors.

Reference

1. Alcazar J, et al. Fat but powerful paradox: association of muscle power and adiposity markers with all-cause mortality in older adults from the EXERNET multicentre study. Br J Sports Med. 2021 Nov;55(21):1204-1211. doi: 10.1136/bjsports-2020-103720.