Fasted Sprint Interval Training Results in Some Beneficial Skeletal Muscle Metabolic, but Similar Metabolomic and Performance Adaptations Compared With Carbohydrate-Fed Training in Recreationally Active Male.
Level 2 - randomized trial
Individual randomized trial
PubMed 36572038 · doi:10.1123/ijsnem.2022-0142
What was done
Recreationally active males underwent sprint interval training (SIT; 4–6 × 30-second Wingate sprints with 4-minute rest intervals) in either a fasted (FAST) or carbohydrate-fed (CHO) state using a double-blind, parallel-group randomized design. Investigators measured skeletal muscle metabolic gene expression and enzyme activity, serum metabolomics, and aerobic/anaerobic performance adaptations acutely and following 3 weeks of training.
What was found
Following acute SIT, FAST elicited favorable upregulation of PDK4 (p = .004), NAMPT (p = .0013), and NNMT (p = .001), alongside increases in pan-acetylation and genes linked to mitochondrial biogenesis, fatty acid oxidation, and NAD+ biosynthesis. After 3 weeks of SIT, NRF2 expression was higher in FAST (p = .029), whereas skeletal muscle pan-acetylation increased only in CHO (p = .033). Maximal citrate synthase activity increased similarly in both groups, and 3-hydroxyacyl-CoA dehydrogenase activity did not change. Specific serum metabolites shifted differently between groups (C3:1 [p = .013] and C4:1 [p = .010] increased in FAST; C16:1 [p = .046] and glutamine [p = .021] increased in CHO), but overall metabolomic profiles were similar. Training-induced gains in anaerobic (p = .898) and aerobic power (p = .249) did not differ between fasted and fed conditions.
Why it matters
While fasted SIT triggers specific molecular signals associated with cellular energy sensing and metabolic regulation, these muscular differences do not translate into superior aerobic or anaerobic performance gains over short-term (3-week) training.
Limits
The abstract does not disclose the sample size or participant attrition. The intervention duration was short (3 weeks), and the cohort was restricted entirely to recreationally active males, limiting generalizability to females and elite athletes.
Cited by
- contradicts Exercising in a fasted state increases mitochondrial adaptations compared to exercising fed.