Journal Title (Medline/Pubmed accepted abbreviation): Br. J. Nutr.
Background: Citrate is a compound found in the body that regulates the activity of many enzymes involved in carbohydrate and fat metabolism. It is thought that hydroxycitrate (HCA) can inhibit some of these metabolism enzymes, thereby favoring fat catabolism (burning) and sparing carbohydrate catabolism.
Hypothesis: Supplementation with HCA will increase the rate of glycogen synthesis when taken after exercise.
Subjects: Eight healthy males, age 22.0 ± 0.3 y
Experimental design: randomized, placebo-controlled, cross-over trial
Treatments: A meal with 70% carbohydrates (2 g CHO/kg body weight) with a 500 mL beverage with or without 500 mg HCA.
Protocol: Before the exercise protocol, muscle biopsies were taken from the vastus lateralis (thigh) muscle and VO2max was determined. On the days of the trial, the participants arrived at the laboratory after an overnight fast. After a 5 min warm-up, they cycled at 75% their previously determined VO2max for 60 min. After exercise, they consumed the meal. Muscle biopsies were acquired immediately after exercise and 3 hrs post-exercise for analysis of muscle glycogen, GLUT4, and FAT/CD36 expression. Blood samples were collected throughout recovery for analysis of blood concentrations of glucose, insulin, non-esterified fatty acids, and glycerol. At least 1 wk later, the participants repeated the protocol with the other treatment.
As a post-exercise supplement, HCA appeared to allow for faster recovery of glycogen stores. These data suggest that HCA may promote fat vs. glucose oxidation, which would tend to preserve glycogen. It would be interesting to see if HCA could improve performance at a subsequent exercise session.