ARS | Publication request: MEAL PALATABILITY, SUBSTRATE OXIDATION AND BLOOD GLUCOSE IN YOUNG AND OLDER MEN

Submitted to: Physiology and Behavior
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 24, 2000
Publication Date: January 1, 2001
Citation: SAWAYA, A.L., FUSS, P.J., DALLAL, G.E., TSAY, R., MCCROY, M.A., YOUNG, V., ROBERTS, S.B. MEAL PALATABILITY, SUBSTRATE OXIDATION AND BLOOD GLUCOSE IN YOUNG AND OLDER MEN. PHYSIOLOGY AND BEHAVIOR. 2001;72:5-12.

Interpretive Summary: Two groups, one of healthy young men, and one of healthy older men, were used to test the effects of a palatable meal versus those of an unpalatable meal on the thermic effect of feeding, substrate oxidation, and circulating glucose and insulin. The differences in reaction of these mechanisms are significant because they are indicators of how quickly hunger returns after a meal, as well as the amount of energy intake at subsequent meals. The subjects had two 2-day visits to the metabolic research unit, and on the second day of each visit consumed (in random order) either a palatable test meal, or an unpalatable test meal (which is the same foods as the palatable ones, presented to the subject after being blended together and freeze dried into biscuit form.) It was found that age group had no effect on these mechanisms, other than to delay the time of peak TEF (thermic effect on feeding). The results suggested that the consumption of a palatable meal is associated with an increased glycemic response and carbohydrate oxidation, which in turn predict an accelerated return of hunger and increased energy intake at subsequent meals.

Technical Abstract: We investigated the effects of food palatability on the thermic effect of feeding (TEF), substrate oxidation and circulating glucose and insulin. Healthy young men (23.4+/-1.0, SD, years, n=10) and older men (69.4+/-1.3, years, n=9) were resident in a metabolic unit for two 2-day study periods. On the second day of each period, they consumed in random order either a palatable test meal containing 2.93 MJ or a nonpalatable control meal containing the same foods in identical amounts but blended and freeze-dried into biscuit form. TEF and respiratory quotient (RQ) were measured over 6 h and blood samples were taken for measurement of glucose and insulin. Age group had no effect on TEF, RQ or circulating glucose other than to delay the time of peak TEF (P<0.002 for both meals). There was no significant effect of meal type on TEF, but RQ and circulating glucose were higher following consumption of the palatable meal (P<0.001 for both parameters). These results suggest that over 6 h postprandial, consumption of palatable foods does not increase TEF, but is instead associated with increased glycemic response and increased carbohydrate oxidation. These changes, combined with previous work on the glycemic index, predict an accelerated return of hunger and increased energy intake at subsequent meals following consumption of palatable vs. control foods. Further studies are needed to examine the possible mechanism for this previously suggested "second meal" effect of diet palatability on energy intake.