Effects of dietary resistant starch on body fat in three different types of mice

Abstract

Resistant starch (RS) is a dietary fermentable fiber, which decreases dietary energy density and causes fermentation in the lower gut. We previously showed dietary RS decreases body fat in rats. The current studies examined the effects in lean and obese mice. In a 12 week study, the effect of RS on body fat was compared in C57Bl/6J (lean) mice to two control diets: regular control diet or the control diet that had equal energy density as the RS diet (EC). All test diets had 7% (wt/wt) dietary fat. In a 16 week study, the effect of RS on body fat was compared with EC in lean mice and two obese mouse models. All mice were fed control or RS diet for 6 weeks with 7% dietary fat. At week 7, the dietary fat was increased to 11% for half of the mice. The pH of cecal contents was measured as an indicator of RS fermentation.ResultsCompared with EC, RS decreased body fat and improved glucose tolerance in lean mice, but not in obese mice. RS decreased RER in both lean and obese mice. Dietary fat did not interfere with these results. The pH of cecal contents in RS fed mice was decreased for lean mice but not for obese mice, implying the impaired RS fermentation in obese mice.Conclusion1) decreased body fat by RS is not simply due to dietary energy dilution in lean mice, and 2) along with their inability to ferment RS, RS fed obese mice did not show decreased body fat. Supported by the NIH.