Calorie restriction has been shown to have “anti-aging” effects in animal models, and calorie restriction-induced weight loss (CRWL) and exercise can both improve insulin sensitivity.

The aim of this study was to investigate the effect of 6-month diet-induced weight loss intervention with or without the addition of exercise training on skeletal muscle mitochondrial respiratory capacity and IS.

Methods: Forty-four older adults with obesity were randomized to one of the following 6-month intervention: Health education (CON: n=14, age=70±4 years, BMI=34±5kg/m2), Diet induced weight-loss (DIWL: n=14, age=70±4 years, BMI=36±5kg kg/m2), or Weight-loss and exercise (WLEX: n=16, age=66±3 years, BMI=37±5kg/m2). CRWL and WLEX participants had a goal of 10% weight-loss through calorie restriction. Subjects in the WLEX group completed a supervised exercise program. Mitochondrial respiratory capacity of permeabilized myofibers from biopsies was evaluated by high-resolution respirometry. Complex I+II supported maximal oxidative phosphorylation (OXPHOS), and maximal uncoupled respiration were evaluated. IS was determined by hyperinsulinemic euglycemic clamps.

Results: IS improved in both CRWL (10.4%) and WLEX (50%) compared to CON (0.7%). However, while mitochondrial respiration was unchanged in the CON and CRWL groups after the 6-month intervention (p>0.05), subjects in the WLEX group presented an increased maximal OXPHOS (PRE: 50.7±10.1 vs. POST: 72.6±17.9 pmol/s*mg) and uncoupled respiration (PRE: 57.2±10.5 vs. POST: 79.6±19.3 pmol/s*mg) after the exercise training.

Conclusions: Despite weight loss and exercise both improving insulin sensitivity, exercise is required to improve mitochondrial respiratory capacity in skeletal muscle of older obese human subjects undergoing calorie restriction-induced weight loss.


G. Distefano: None. R. Standley: None. E.A. Carnero: None. P.M. Coen: None. R.B. Vega: None. B.H. Goodpaster: None.

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