Plasma and urinary carnitine of obese subjects on very-low-calorie diets.

We evaluated the differential effects of feeding two very-low-calorie diets upon the fractions of plasma and urinary carnitine in obese females. Ten subjects received either diet D1, a 420 kcal/day formula diet, or diet D2, a 500-600 kcal/day meat/fish/poultry diet. Plasma and urinary carnitine levels were determined at the start of the study. After 1 month, plasma carnitine levels were obtained; at 2 months, both plasma and urinary carnitine levels were obtained. Subjects receiving diet D2 showed significantly higher levels of plasma total carnitine over the course of the study (p less than 0.05). Plasma short-chain acylcarnitine esters increased and free carnitine declined significantly in both groups during the study period. Subjects receiving D1 excreted significantly less urinary carnitine than those receiving D2. We conclude that long-term ingestion of very-low-calorie diets causes alterations in plasma carnitine metabolism.