Endocrine markers of semistarvation in healthy lean men in a multistressor environment.
Level 3 - non-randomized controlled study
Prospective non-randomized comparative study evaluating two dietary deficit levels in military cohorts.
PubMed 10797147 · doi:10.1152/jappl.2000.88.5.1820
What was done
Evaluated endocrine and metabolic responses to semistarvation in 97 healthy young male volunteers during an 8-week US Army Ranger course combining caloric deficits, heavy physical workload, sleep deprivation, and thermal strain. Participants underwent four repeated cycles of restricted energy intake and refeeding across two groups: group 1 (n = 49, average deficit 1,200 kcal/day) and group 2 (n = 48, average deficit 1,000 kcal/day). Serum hormones (T3, testosterone, IGF-I, LH, cortisol, insulin) and cholesterol were measured across time and through refeeding.
What was found
After 8 weeks, group 1 reached minimal body fat, serum T3 fell below normal (78 ± 20 ng/dl), testosterone approached castrate levels (4.5 ± 3.9 nmol/l), IGF-I dropped by half (75 ± 25 µg/l), and cholesterol increased from 158 ± 31 to 217 ± 39 mg/dl. Reductions in insulin led to higher binding protein levels, further reducing bioavailable T3 and testosterone. Refeeding rapidly restored T3, testosterone, and IGF-I despite the continuation of non-dietary stressors. Group 2's higher intake attenuated subclinical hypothyroidism and hypercholesterolemia, while luteinizing hormone suppression persisted in both groups.
Why it matters
Shows that testosterone, T3, and IGF-I are sensitive, rapidly reversible markers of acute energy deficit that respond primarily to caloric intake rather than co-occurring operational stressors like sleep loss and heavy exertion, whereas cholesterol and cortisol reflect chronic energy depletion.
Limits
The study sample was entirely young, highly fit, lean military males, precluding generalization to females, older adults, or clinical populations. Group allocation was not described as randomized, and individual effects of concurrent stressors (sleep loss, thermal strain, physical exertion) could not be entirely separated from energy deficit.
Cited by
- supports In men with 15% body fat or less, cutting calories below maintenance for extended periods (e.g., several weeks) reduces testosterone and free testosterone levels.