Dietary Fat Chain Length, Saturation, and PUFA Source Acutely Affect Diet-Induced Thermogenesis but Not Satiety in Adults in a Randomized, Crossover Trial

Abstract

Structural differences in dietary fatty acids modify their rate of oxidation and effect on satiety, endpoints that may influence the development of obesity. This study tests the hypothesis that meals containing fat sources with elevated unsaturated fats will result in greater postprandial energy expenditure, fat oxidation, and satiety than meals containing fats with greater saturation. In a randomized, 5-way crossover design, healthy men and women (n = 23; age: 25.7 ± 6.6 years; BMI: 27.7 ± 3.8 kg/m²) consumed liquid meals containing 30 g of fat from heavy cream (HC), olive oil (OO), sunflower oil (SFO), flaxseed oil (FSO), and fish oil (FO). Energy expenditure and diet-induced thermogenesis (DIT) were determined by metabolic rate over a 240 min postprandial period. Serum concentrations of ghrelin, glucose, insulin, and triacylglycerol (TAG) were assessed. DIT induced by SFO was 5% lower than HC and FO (p = 0.04). Energy expenditure and substrate oxidation did not differ between fat sources. Postprandial TAG concentrations were significantly affected by fat source (p = 0.0001). Varying fat sources by the degree of saturation and PUFA type modified DIT but not satiety responses in normal to obese adult men and women.

Keywords: diet-induced thermogenesis; fat oxidation; polyunsaturated fatty acids; respiratory exchange ratio; satiety; thermic effect of food.

Figure 1

CONSORT diagram indicating the number of participants completing the initial study survey, invited to an information meeting for consent, screened, enrolled, randomized into a treatment order, and completing each of the five treatment arms.

Figure 2

Metabolic rate (A), DIT (B), and RER (C) in an acute study of five dietary fat sources on satiety and energy expenditure in normal to obese participants. Values are the mean ± SD, n = 23 except HC, n = 20. Metabolic rate data (A) were compared using a linear mixed model was used with Tukey-Kramer multi-comparison adjustment. The DIT data (B) were compared using a linear mixed model was used with a Tukey-Kramer multi-comparison adjustment. The RER data (C) were compared using a two-way interaction mixed ANOVA with repeated measures was performed with a Tukey’s multiple comparison adjustment. Labeled means for each treatment (B) without a common letter differ, p < 0.05. DIT, diet-induced thermogenesis; FO, fish oil; FSO, flaxseed oil; HC, heavy cream; OO, olive oil; RER, respiratory exchange ratio; SFO, sunflower seed oil.

Figure 3

Hunger (A), fullness (B), satisfaction (C), and desire to eat (D) from an acute test of five dietary fat sources in normal to obese participants. Values are means ± SD; n = 23 except HC, n = 21. Data were compared using a two-way interaction mixed ANOVA with repeated measures with a Tukey’s multiple comparison adjustment. FO, fish oil; FSO, flaxseed oil; HC, heavy cream; OO, olive oil; SFO, sunflower seed oil.

Figure 4

Ghrelin (A), TAG (B), insulin (C), and glucose (D) responses to an acute test of five dietary fat types on satiety and energy needs in normal to obese participants. Labeled means at each time point without a common letter differ, p < 0.05. A two-way interaction mixed ANOVA with repeated measures was performed with Tukey’s multiple comparison adjustment as a post hoc test. Values are means ± SD; n = 23 except for HC n = 21, insulin HC n = 19, and insulin FO n = 22. FO, fish oil; FSO, flaxseed oil; HC, heavy cream; OO, olive oil; SFO, sunflower seed oil.