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To the Editor: In the study of cardiorespiratory fitness and adiposity by Dr Sui and colleagues,¹ a cohort of 2603 adults older than 60 years was followed up for a mean of 12 years. The authors evaluated the predictive association of measures of adiposity and fat distribution as well as cardiorespiratory fitness with mortality. Fitness and body mass index predicted mortality independently of several established risk factors. Most notably, the effect of fitness was independent of total and abdominal adiposity. To explain this relationship, the authors hypothesize that high fitness levels indicate improved skeletal muscle function, such as strength, power, and endurance.

Other mechanisms possibly explain the relationship between fitness and longevity in older adults. High cardiorespiratory fitness is strongly associated with high mitochondrial function.² Increased mitochondrial function is related to low ectopic fat accumulation in liver and skeletal muscle. These relationships are independent of total adiposity.² Nonalcoholic fatty liver . . . [Full Text of this Article]

Norbert Stefan, MD
norbert.stefan@med.uni-tuebingen.de

Konstantinos Kantartzis, MD; Hans-Ulrich Häring, MD
Department of Internal Medicine
Division of Endocrinology, Diabetology, Vascular Medicine, Nephrology, and Clinical Chemistry
University of Tübingen
Tübingen, Germany

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