Effects of fat adaptation on glucose kinetics and substrate oxidation during low-intensity exercise.

This research article explores how adapting to a fat-supplemented diet affects the metabolism of carbohydrates and fats in trained horses during low-intensity exercise, observing a decrease in glucose production and utilisation, and an increase in the rate of lipid oxidation after spending 5-10 weeks on the fat-supplemented diet.

Research Design and Methodology

• The study was conducted with a sample size of five mature Arabian horses. The effects of diet on their carbohydrate and fat metabolism during low-intensity workouts were observed.
• The research was designed as a crossover study employing two dietary periods, each lasting ten weeks: a control diet and a fat-supplemented diet.
• The control diet included 7% digestible energy derived from fat, while the fat-supplemented diet comprised 29% digestible energy from fat.
• The effect of the dietary shift was evaluated by having the horses complete exercise tests at the beginning of the period, and after five and ten weeks on each diet. These exercises lasted 90 minutes and were carried out at a speed calculated to elicit 35% of the maximum oxygen volume (VO2max).
• Variables of oxygen consumption (VO2), carbon dioxide production (VCO2), and respiratory exchange ratio (RER) were measured at 15-minute intervals in the study.

Research Findings

• Following a period of 5 to 10 weeks on a fat-supplemented diet, the horses showed a change in metabolic responses during low-intensity exercises.
• There was over 30% reduction in the production and utilisation of glucose after the change in diet.
• Further, the study recorded a decrease in the respiratory exchange ratio, indicating a reduced rate of carbohydrate metabolism.
• The research observed a decrease in the estimated rate of whole-body carbohydrate utilization, suggesting a decrease in dependence on carbohydrates for energy during low-intensity exercise.
• Concomitantly, the research reported an increase in the rate of lipid oxidation throughout the body, suggesting that body fat was being burned more frequently for energy during low-intensity workouts.