• A randomized, double-blind, placebo-controlled, parallel-arm trial. • 68 overweight adults (35–75 yrs) with pre-diabetes were randomized to consume 45 g/d of HAM-RS2 or an isocaloric amount of the RDS amylopectin (control) for 12 wks. • HbA1c, insulin sensitivity, insulin secretion, ectopic fat, and markers of inflammation. The gene discussed is INS; the disease is diabetes mellitus.