Weight loss-independent changes in human growth hormone during water-only fasting: a secondary evaluation of a randomized controlled trial.
Level 2 - randomized trial
Secondary analysis of a randomized crossover trial
PubMed 39991046 · doi:10.3389/fendo.2024.1401780
What was done
In a secondary analysis of a randomized crossover trial, 30 apparently healthy adults (20 females, 10 males) were assigned by Latin square to either 24 hours of water-only fasting followed by 24 hours of ad libitum eating, or the reverse sequence. Human growth hormone (HGH), body weight, and metabolic markers were measured at baseline and at the conclusion of each 24-hour period.
What was found
Baseline median HGH was 0.50 ng/mL in females and 0.04 ng/mL in males, correlating inversely with weight, glucose, insulin, and triglycerides. Fasting-induced changes in HGH did not correlate with weight loss (r = 0.01, p = 0.98), though they correlated with changes in glucose, hemoglobin, and IGF-1. Participants with lower baseline HGH (females ≤0.15 ng/mL, males ≤0.05 ng/mL) experienced a significantly higher median percentage surge in HGH compared to those with higher baseline levels (1,225% vs. 50.3%, p < 0.001) and showed a trend toward greater HOMA-IR reduction (median change: -6.15 vs. -1.35, p = 0.08).
Why it matters
The findings indicate that the acute elevation of growth hormone during short-term water fasting is a direct physiological response to nutrient deprivation rather than a byproduct of acute weight loss.
Limits
The sample size was small (N=30) and skewed toward female participants (20 vs. 10 males). As a secondary post-hoc analysis examining a single 24-hour fasting window, the study did not measure pulsatile 24-hour HGH secretory profiles or long-term clinical outcomes.
Cited by
- supports Exercise, deliberate heat exposure, and intermittent fasting have all been shown to increase growth hormone.