Cardiac effects of starvation and semistarvation diets: safety and mechanisms of action.

A major concern with the use of starvation or semistarvation diets for weight reduction in severely obese people has been the reports of sudden death due to ventricular arrhythmias. Obesity per se is associated with cardiovascular changes, including left ventricular hypertrophy and prolongation of the QT interval. With weight loss, the mass of the heart and left ventricle decrease, but some signs of left ventricular dysfunction remain. The effect of weight loss on the electrocardiogram abnormalities of obesity appears to depend upon diet duration and upon whether protein and mineral nutritional status is maintained. Copper, potassium, and magnesium deficiencies may play important roles in promoting an electrically unstable heart. Stress, by eliciting autonomic imbalance, may act upon an electrically unstable heart to provoke acute arrhythmias in a subset of the obese population with QT interval prolongation.