Oat, Wheat or Corn Cereal Ingestion before Exercise Alters Metabolism in Humans

Abstract

This study was designed to determine metabolic and physical performance responses to ingestion of pre-exercise meals with different macronutrient and fiber profiles. Twelve physically active subjects (6 males and 6 females) were used to investigate the metabolic and physical performance consequences of consuming pre-exercise meals consisting of oat, corn, or wheat cereals. A fasting trial served as the control, and all subjects received each treatment in a Latin-square design. Blood samples were drawn before and 85 min after meal ingestion, during 90 min of cycling exercise (60% VO2peak), after a 6.4 km performance ride, and during 60 min of recovery. Expired air samples were collected to determine nutrient utilization. Resting carbohydrate oxidation rates and plasma insulin concentrations after oat ingestion were less than after wheat, and corn and wheat ingestion, respectively (P < 0.05). During exercise, the change in plasma glucose from pre-exercise was greater after consuming wheat and corn compared with oat (P < 0.05), and it was inversely related to pre-exercise plasma insulin concentration (r = -0.55, P = 0.0001). Plasma free fatty acid concentrations were inversely related to plasma lactate concentrations (r = -0.58, P = 0.0001). Free fatty acid concentrations and fat oxidation were greater in fasting trials than all others, but performance ride times did not differ among treatments. Plasma branched-chain amino acid concentrations resembled their respective meal profiles throughout exercise, the performance ride, and recovery. These results indicate that pre-exercise meal composition can influence glucose homeostasis during early exercise and plasma branched-chain amino acid concentrations over a substantial range of metabolic demands.

Effects of fasted vs fed‐state exercise on performance and post‐exercise metabolism: A systematic review and meta‐analysis

“…FFA concentrations were elevated in 38% of studies where it was measured in the fasted vs fed condition . A large fasting effect was observed for post‐exercise circulating FFA ( k = 36; g = 0.7 [0.1:1.2]; Z = 2.27; P = .023).…”

“…Regarding studies showing a beneficial effect of acute pre‐exercise feeding on aerobic exercise performance, 1 provided a mixed meal, 1 implemented a high‐carbohydrate meal, and 5 provided predominantly carbohydrate as an energy source . A further 7 studies evaluated markers of shorter duration (<60 minutes) aerobic performance . Of these, 57% found no differences in performance between fasted and fed conditions .…”

“…A further 7 studies evaluated markers of shorter duration (<60 minutes) aerobic performance . Of these, 57% found no differences in performance between fasted and fed conditions . The remaining studies determined that pre‐exercise feeding bolstered time trial performance .…”

Effects of exercising before breakfast on the health of T2DM patients—A randomized controlled trial

“…One explanation of why training in the fasted state had no superior effects in the present study could be related to the fact that T2DM at an early stage is often accompanied by hyperinsulinemia . Some previous studies indicate that there are lower blood insulin levels, elevated blood free fatty acid concentrations as well as increased fat oxidation rates in healthy subjects during acute exercise in the fasted state . This led to the assumption that repeated exercise in the fasted state could be instrumental in improving oxidative metabolism and glycemic control (lipotoxicity‐induced insulin resistance) in the long‐term.…”

“…It has been demonstrated that acute exercise in the fasted state can be accompanied by elevated blood free fatty acid concentrations and increased fat oxidation rates in healthy subjects . Furthermore, some studies involving healthy subjects indicate that physical training (regular physical exercise) in the fasted state can induce greater adaptations than in the fed state (eg, increased glucose tolerance, increased basal muscle glycogen concentrations, and up‐regulation of components of the oxidative metabolism) .…”