Cardiac effects of caloric restriction-mechanisms and potential hazards

The heart is not spared from the catabolic effects of undernutrition, but is subject to the same degree of weight loss as skeletal muscle. Pumping performance, however, is not reduced in proportion to myocardial wasting and thus functional protection prevents failure of the hypotrophic heart. In animal experiments, no major qualitative changes in myocardial composition apart from reduced myosin ATPase activity have been found. This reduction in ATPase activity might be associated with down-regulation of thyroid hormones and the development of insulin resistance and serve as an energy saving adaptation. Increased cardiac sensitivity to adrenergic stimulation may also constitute a means to increase heart performance in situations with augmented circulatory demands. On the other hand, increased sensitivity and maximum response to adrenergic stimulation might render the heart more susceptible to arrhythmia, and thus explain sudden unexpected death following rapid weight loss.