Ingestion of a high molecular weight modified waxy maize starch alters metabolic responses to prolonged exercise in trained cyclists

Abstract

We examined whether ingestion of a modified waxy maize starch (WMS) designed to have a low glycemic impact would alter metabolic and hormonal responses to prolonged cycling compared to Maltodextrin. Ten male cyclists (n: 9, age: 30 2 y, weight: 79.2 2.1 kg, VO2peak: 4.7 0.1 L/min, training: 7.5 1.3 y) fasted for 12 h before cycling for 150 min @ 70% VO2peak. Before and after exercise, participants ingested 1g/kg of either WMS or Maltodextrin while providing blood and expired gas samples every 15 and 30 min, respectively, before, during, and following exercise. In a crossover fashion, identical testing was completed one week later. There was a rapid increase in blood glucose immediately after the ingestion of Maltodextrin pre‐ and post‐exercise, which was significantly attenuated by WMS (P < 0.05). In a similar manner, serum insulin levels were also significantly lower after ingestion of WMS (peak = 2.5 ìIU/ml) compared to Maltodextrin (peak = 20.3 ìIU/ml). WMS was associated with greater fat breakdown and oxidation during exercise and recovery as indicated by significantly increased serum non‐esterified fatty acids and glycerol levels and a trend for lower respiratory exchange ratios compared to Maltodextrin. Ingestion of a low glycemic modified waxy maize starch prior to prolonged submaximal cycling blunted the initial spike in blood glucose and insulin while enhancing breakdown and oxidation of fat.

Impact of Starch Gelatinization on Digestibility and Human Health

“…It has been shown in trained cyclists to blunt the spike in blood glucose and insulin whilst increasing the break-down of fat compared to, for example, maltodextrin. [80][81][82]…”