‘Fat but Fit’ Paradox – Unravelling the Truth

Introduction

Obesity is now recognized as a serious chronic disease; in my post titled Is obesity a disease or a risk factor for other conditions? I had discussed the magnitude of obesity and why obesity is associated with so much ill-health. However, there are no easy solutions to obesity and managing your body weight is challenging at the best of times. In my post titled Weight Loss Maintenance After Weight Loss, I had discussed how over the long term, the vast majority of individuals regain the weight they have lost and that this relapse has a strong physiological basis and is not simply the result of the voluntary resumption of old habits. Some evidence suggests, however, that a high cardiorespiratory fitness (CRF) might mitigate the detrimental effects of excess body weight on cardiometabolic health, termed the ‘fat but fit’ paradox.

Recognition of the ‘fat but fit’ paradox

In my post, Complications of obesity: the mother of all diseases, I had discussed the various health complications associated with obesity.  However, accumulating evidence over the years suggests that being physically fit might attenuate some of the deleterious health consequences of obesity independently of some key potential confounders. About 3 decades ago, a study titled ‘Physical Fitness and All-Cause Mortality: A Prospective Study of Healthy Men and Women’ published in the Journal of the American Medical Association in Nov 1989, brought into focus the detrimental role of fitness (cardiorespiratory fitness [CRF]) vis-à-vis fatness on health, specifically all-cause mortality and CVD-related mortality. This longitudinal study followed up 10,224 men and 3120 women for slightly more than 8 years. The study found that better CRF, as measured by a maximal exercise test, was associated with decreased all-cause mortality in both sexes. Based on the maximal treadmill test, participants were stratified into quintiles of fitness categories. Age-adjusted all-cause mortality rates declined across physical fitness quintiles from 64.0 per 10,000 person-years in the least-fit men to 18.6 per 10,000 person-years in the most-fit men (fat but fit). Corresponding values for women were 39.5 per 10,000 person-years to 8.5 per 10,000 person-years. Lower mortality rates in higher fitness categories also were seen for cardiovascular disease and cancer of combined sites. Higher levels of physical fitness appear to delay all-cause mortality primarily due to lowered rates of cardiovascular disease and cancer.

A couple with obesity exercising together, i.e. fat but fit.
A couple with obesity exercising together – ‘fat but fit’.
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