Lower extremity strength, systemic inflammation and all-cause mortality: Application to the "fat but fit" paradigm...

No study has applied the "fat-but-fit" paradigm with respect to muscular strength as an index of fitness, despite muscular strength being independently associated with functional ability and mortality.

To examine the relationship between lower extremity muscular strength, C-reactive protein (CRP), and all-cause mortality among normal weight, overweight and obese individuals.

Data from the 1999-2002 NHANES were used (N=2740 adults; ≥ 50 years). CRP values were obtained from a blood sample. Lower body isokinetic knee extensor strength (IKES) was assessed using a Kin Kom MP isokinetic dynamometer. Participant data was linked to death certificate data from the National Death Index to ascertain all-cause mortality status. Participants were classified, based on body mass index (BMI) and strength as: normal weight and unfit (<75th IKES percentile); overweight and unfit; obese and unfit: normal weight and fit (≥ 75th IKES percentile); overweight and fit; and obese and fit.

Independent of physical activity and other confounders, compared to those who were normal weight and unfit, unfit overweight (β=.14, p=0.009), unfit obese (β=.33, p<0.001), and obese and fit (β=.17, p=0.008) participants, had higher CRP levels. However, there was no difference in CRP levels between normal weight and unfit participants and overweight and fit participants (β=0.04, p=0.35). Compared to normal weight unfit adults, overweight fit (HR=0.28; 95% CI: 0.11-0.70; p=0.008) adults had a lower hazard rate for all-cause mortality.

These finding suggest that increased lower body strength, independent of physical activity, may reduce premature all-cause mortality and attenuate systemic inflammation among overweight adults.