|Van Loan, Marta|
Submitted to: Journal of Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/4/2008
Publication Date: 12/23/2008
Publication URL: http://jn.nutrition.org/content/139/2/222.full.pdf+html
Citation: Smilowitz, J., Wiest, M.M., Watkins, S.M., Teegarden, D., Zemel, M.B., Van Loan, M.D., German, B.J. 2008. Changes in lipid metabolism during energy restriction interventions. Journal of Nutrition. 139(2):222-9. Interpretive Summary: Increased blood lipids such as cholesterol and triglycerides have been associated with increased risk for heart disease as well as obesity. Diets that restrict caloric intake and reduce body weight may improve blood lipids. Our study examined whether the components of the weight-reduction diet, specifically supplemental calcium, and dairy foods which are high in mono-unsaturated fats (MUFA), would improve blood lipids compared to a control diet with less than 600 mg/d of calcium for 63 overweight individuals. Results showed that blood lipids reflected dietary intake of mono-unsaturated fats (MUFA) and poly-unsaturated fats (PUFA), but there was no association between saturated fats in the diet and blood lipid levels. The average MUFA intake of the diet was related to changes in lean mass; the higher the MUFA intake the less lean mass was lost, and the more body fat was lost. Further investigation of blood lipid metabolism during weight loss requires controlled feeding studies designed to control the type and amount of dietary fat intake.
Technical Abstract: The objective of this analysis of a subset from a multi-center 12 wk weight-loss trial was to determine if calcium supplementation or dairy food consumption during energy restriction changed circulating lipids compared with an energy-restricted placebo group. Overweight adults (n = 63) were randomized to one of three intervention groups: 1) placebo (<600 mg/d calcium intake); 2) 900 mg/d calcium supplement; and 3) 3 to 4 servings of dairy products/d plus a placebo supplement. Dairy product consumption led to a significantly higher mean change in % lean mass (LM) (+3.4% vs. +1.4%) and decrease in % body fat (BF) (-3.5% vs. -1.6%) compared to the calcium group. There were no changes in circulating fatty acids of cholesterol ester (CE), free fatty acids (FFA), phosphatidylcholine (PC) and triacylglycerol (TAG) in response to treatment. Stepwise regression found partial correlations between MUFA intake (% of fat) and circulating lipids CE 18:1(n-9) (r = 0.44, P< 0.001) and PC 18:1(n-9) (r = 0.39, P< 0.01); and reported mean PUFA intake with CE 20:4(n-6) (r = -0.29, P< 0.05) at 12 wk. As a percentage of energy intake, MUFA was associated with changes in % LM (r = -0.36, P< 0.01) and % BF (r = 0.39, P< 0.01). PUFA intake was associated with the % change in waist circumference (r = 0.27, P< 0.05). Saturated fat intake was not associated significantly with any anthropometric change. Long-term feeding studies that control for diet composition should be conducted to determine the mechanisms by which dietary fat composition influences changes in body composition during energy restriction.