Journal Name:
Clin. Nutr.
Article Title:
Acute effects of three high-fat meals with different fat saturations on energy expenditure, substrate oxidation and satiety.
Date Written:
2009
Volume:
28
Number:
NA
Page:
39
Author(s):
Casas-Agustench, P.; López-Uriarte, P.; Bulló, M.; Ros, E.; Gómez-Flores, A.; Salas-Salvadó, J.
Article:
Olive oil is an important component of the Mediterranean diet and is associated with protection from myocardial infarction and total mortality. The oil has a low content of saturated fatty acids (SFA) but a high content of unsaturated fatty acids, mainly monounsaturated fatty acids (MUFA). Canola oil has similar properties. However, because these are oils, the common perception that they provide excess energy and thus promote obesity has had a negative effect on their image. Recently, high intakes of olive oil were not associated with weight gain or the risk of overweight or obesity in a prospective study of a large Mediterranean cohort. It has been suggested that olive oil consumption is associated with increases in satiety, thermogenesis, and fat oxidation. Few studies designed specifically to evaluate the effect of olive oil consumption on energy balance and body weight, or on thermogenesis, substrate oxidation and satiety have been performed.
The aim of this study was to assess the effects of the acute consumption of three isocaloric high-fat meals differing in fat quality on resting metabolic rate (RMR) and postprandial thermogenesis, substrate oxidation and satiety in healthy men. Twenty-nine healthy men aged between 18 and 30 years participated in a randomised crossover trial comparing the thermogenic effects of three isocaloric meals: high in polyunsaturated fatty acids from walnuts, high in monounsaturated fatty acids from olive oil, and high in saturated fatty acids from fat-rich dairy products. Indirect calorimetry was used to determine resting metabolic rate, respiratory quotient, five hour postprandial energy expenditure and substrate oxidation. Satiety was estimated by using visual analogue scales and measuring caloric intake in a subsequent ad libitum meal.
Five hour postprandial thermogenesis was higher by 28% after the high-polyunsaturated meal and by 23% higher after the high monounsaturated meal compared with the high-saturated meal. Fat oxidation rates increased nonsignificantly after the two meals rich in unsaturated fatty acids and decreased nonsignificantly after the high-saturated fatty acid meal. Postprandial respiratory quotient, protein and carbohydrate oxidation, and satiety measures were similar among meals.
Fat quality determined the thermogenic response to a fatty meal but had no clear effects on substrate oxidation or satiety. These results showing that intake of vegetable fat induces a higher thermogenic effect than that of animal fat derived from fat-rich dairy products concur with recent acute studies. Differences in substrate utilization and thermogenesis after intake of meals with various types of fat might be explained by several mechanisms, such as dissimilar changes in gastric emptying, sympathetic nervous activity, or expression uncoupling protein (UCP) genes. The administration of olive oil for example, upregulates UCP genes expression in adipose tissue and muscle of rats, thus inducing changes in total oxygen consumption.
No differences in satiety after the consumption of meals high in PUFA, MUFA or SFA were noted. It is possible that the amount of fat used in the test meals were not sufficient. The source of fat may be more important for satiety than the type of fat. If thermogenesis was higher after a meal rich in unsaturated vegetable fat in comparison with SFA from dairy products and this was sustained over time, a change in the type of dietary fat consumed within a diet relatively high in vegetable fat might help curb weight gain. However, long-term studies will be necessary in order to demonstrate beneficial effects of vegetable sources of unsaturated fat compared to animal fat on energy balance.
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