Effect of catecholamine replacement with levodopa on the metabolic response to semistarvation.

The resting metabolic rate (R.M.R.) falls on energy restriction in association with a fall in the circulating calorigenic hormones, triiodothyronine (T3) and noradrenaline. Levodopa, a precursor of catecholamines, was given to obese subjects receiving a low-energy diet in an attempt to prevent the reduction in catecholamine turnover and noradrenaline levels. Levodopa prevented the fall in R.M.R. despite the expected decline in T3 levels on semistarvation. These results suggest that changes in catecholamine metabolism are important in determining adaptive changes in metabolic rate.