The contribution of protein synthesis to thermogenesis in man

There is ample evidence in man that there is some process which results in an increase or decrease in resting metabolic rate with over- or under-feeding. The change occurs within a few days of altering the plane of nutrition, and cannot be accounted for by changes in body composition. There is also agreement that metabolic rate increases after a meal, and more so after a meal of protein. The reasons for these changes are not well understood, but a suggestion made some time ago that they reflect changes in the rate of protein synthesis is still plausible. However, all thermogenesis cannot be accounted for by increased protein synthesis: after a glucose load metabolic rate increases but the rate of protein synthesis decreases. Within the last five years there have been amazing improvements in technology for measurement of protein turnover in man using stable isotopes. In the next five years the careful application of these techniques should enable us to measure exactly the contribution of protein synthesis to thermogenesis in man.