Interval training in the fed or fasted state improves body composition and muscle oxidative capacity in overweight women.
Level 2 - randomized trial
Individual randomized controlled trial
PubMed 23723099 · doi:10.1002/oby.20379
What was done
Sixteen overweight or obese women (mean age 27 ± 8 years, BMI 29 ± 6 kg/m², VO2peak 28 ± 3 ml/kg/min) were assigned to perform 18 sessions of high-intensity interval training (10 × 60-s cycling efforts at ~90% maximal heart rate with 60-s recovery) over 6 weeks in either a fasted (FAST, n = 8) or fed (FED, n = 8) state. Authors measured body composition by dual energy X-ray absorptiometry, muscle oxidative capacity via maximal activities of citrate synthase and β-hydroxyacyl-CoA dehydrogenase from resting biopsies, and glycemic control.
What was found
No significant differences were found between the FAST and FED groups for any measured variable. Across all participants, body mass did not change, but training led to lower percent fat in abdominal, leg, and whole-body regions (P ≤ 0.05) and increased fat-free mass in leg and gynoid regions (P ≤ 0.05). Muscle biopsies showed increased maximal activities of citrate synthase and β-hydroxyacyl-CoA dehydrogenase (P ≤ 0.05). Insulin sensitivity did not change overall, though change in insulin area under the curve correlated with change in abdominal percent fat (r = 0.54, P ≤ 0.05).
Why it matters
This study shows that short-term low-volume interval training improves body composition and muscle oxidative capacity in overweight women regardless of whether exercise is performed in the fed or fasted state.
Limits
The sample size was very small (n = 8 per group), limiting statistical power to detect small differences between conditions. The study included only overweight/obese women over a 6-week duration, and specific numerical effect estimates and variance metrics for group differences were not reported in the abstract.
Cited by
- context Performing endurance exercise in a fasted state enhances mitochondrial adaptations compared to a fed state.