In a recent study (19), 1-day supplementations of resistant starch with long-chain inulin increased distal colonic fermentation (as shown by increased circulating butyrate and breath hydrogen the next morning), which was coincident with increased energy expenditure, circulating PYY, and improved insulin sensitivity in lean men, but not in men with prediabetes and overweight/obesity. The gene discussed is INS; the disease is obesity due to melanocortin 4 receptor deficiency.