Polyunsaturated:saturated ratio of diet fat influences energy substrate utilization in the human

In order to examine the effect of dietary long chain fatty acid composition on energy substrate utilization, basal metabolism rate (BMR) and the thermogenic effect of food (TEF) were measured in eight subjects consuming diets varying only in diet fat polyunsaturated:saturated (P:S) ratio. Subjects consumed the low P:S (0.241 +/- 0.02) and high P:S (1.65 +/- 0.28) ratio diets for seven days using a crossover design. Fat and carbohydrate oxidation during BMT and TEF over 230 minutes after a breakfast meal were determined on days 1 and 7 of each diet period using open circuit respiratory gas exchange. On day 7, BMR respiratory quotient was reduced (P less than .05) for the low P:S (0.826 +/- 0.005) compared with high P:S (0.853 +/- 0.014) ratio diet, resulting in an increased basal fat oxidation rate with low P:S (0.074 +/- 0.006 g/min) compared with high P:S (0.059 +/- 0.008 g/min) ratio diet feeding. The cumulative contribution of fat oxidation to TEF on day 7 was lower (P less than .01) for the low P:S (1.35 +/- 1.6 g) compared with high P:S (6.49 +/- 0.8 g) ratio diets. This was paralleled by opposite differences (P less than .05) in the contribution of carbohydrate oxidation to TEF (21.0 +/- 3.0 g and 13.1 +/- 3.4 g, respectively, for each diet treatment). On day 1 in subjects switching from either home and alternate test diets, and on day 7, caloric expenditure of TEF after low P:S was not statistically lower compared to the high P:S ratio diet.(ABSTRACT TRUNCATED AT 250 WORDS)