Resistant starch reduces abdominal fat more than energy dilution with nonfermentable fiber

Abstract

This study was designed to compare a resistant starch (RS) diet with an equal energy control diet to determine if the effects of RS are due to energy dilution and when these effects first appear. The time course study had three periods (1, 3 and 5 wks) comparing fermentable RS diet (3.3 kcal/g, National Starch) with non-fermentable cellulose (energy control, EC, 3.3 kcal/g) diet. Thirty (n=5/period) 8 week old male Sprague Dawley rats were used. The study had two independent variables (diet and period), but pooled data for diet effects (n=15/diet) are shown. RS rats had lower abdominal fat (RS, 4.4; EC 5.9±0.3 g), and pH (RS, 6.32; EC, 8.38±0.11), but higher total short chain fatty acids (SCFA; RS, 1.27; EC 0.2±0.1 mol), acetate (RS, 0.6; EC, 0.1± 0.05 mol), propionate (RS, 0.35; EC, 0.05±0.04 mol) and butyrate (RS, 0.29; EC, 0.02±0.03 mol) than EC rats (lsmeans±SEM). RS rats had higher plasma PYY (RS, 20.5; EC, 2.5±2 pg/100ul) and gene expression relative to cyclophilin for PYY (RS, 0.81; EC, 0.37±0.08) and proglucagon (GLP-1; RS, 2; EC, 0.24±0.28) than EC rats. Amount of food ingested (RS, 447; EC, 458±8 g) as well as metabolizable energy intake (RS, 1460; EC, 1499±25g) were similar for the two groups. The effect of lower abdominal fat for rats fed RS was beyond that of simple energy dilution with cellulose. Fermentation of RS was active after one week as was the higher plasma PYY and PYY and proglucagon gene expression. We hypothesize that RS affects energy balance through a signaling mechanism involving SCFA induction of PYY, and GLP-1.