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Nutrient Physiology, Metabolism, and Nutrient-Nutrient Interactions

Dietary Starch Type Affects Body Weight and Glycemic Control in Freely Fed but Not Energy-Restricted Obese Rats^1–3,

⁴ Nutrition Research Division, Bureau of Nutritional Sciences, Food Directorate, Health Products and Food Branch, Health Canada, AL 2203E, Ottawa, ON, K1A 0K9 Canada; and ⁵ Agriculture and AgriFood Canada; Guelph Food Research Centre, Guelph, ON, N1G 5C9 Canada

This study comprised 2 experiments that tested the hypothesis that a high-amylose starch diet (AMO) would improve body weight and glycemic control relative to a high-amylopectin starch diet (AMN) in rats with diet-induced obesity. After inducing obesity with a high-fat and -energy diet (Expt. 1), male Sprague-Dawley rats (n = 46) were divided into 4 groups and given free or restricted access to either an AMN or an AMO diet for 4 wk (Expt. 2). After 3 wk, rats from each group underwent an oral glucose tolerance test. At the end of the experiment, food-deprived rats were killed by decapitation and blood and tissues were collected for analyses. AMO led to lower total energy intake, weight gain, fat pad mass, and glycemic response but higher insulin sensitivity index than AMN, only when consumed ad libitum (AL) (P < 0.05). AMO led to higher glucagon-like peptide-1 and peptide YY responses and mRNA levels, independent of feeding paradigm (P < 0.01). The mRNA levels of key neuropeptide systems involved in the regulation of food intake were affected only by energy restriction. On the other hand, AMO resulted in higher expression of uncoupling protein-1 in the brown adipose tissue than AMN in rats that consumed food AL (P < 0.05). The effects of AMO appear to be mediated by its high resistant starch content rather than its glycemic index. We conclude that starches high in AMO can be effective in weight and glycemic control in obesity.

^* To whom correspondence should be addressed. E-mail: alfred_aziz{at}hc-sc.gc.ca.

Manuscript received 22 May 2009. Initial review completed 25 May 2009. Revision accepted 28 July 2009.

Published online 19 August 2009.