Humans with obesity exhibit impaired circulating total, but not free, IGF-1 response to acute endurance exercise.
Level 3 - non-randomized controlled study
Non-randomized controlled comparative physiological cohort study
PubMed 40574473 · doi:10.14814/phy2.70436
What was done
Participants with and without obesity performed a 45-minute cycling session at 65% of heart rate reserve. Blood samples were collected before exercise, at 15 and 40 minutes during exercise, and 15 minutes post-exercise to measure serum levels of total IGF-1, free IGF-1, IGFBP-1, IGFBP-3, growth hormone, and insulin.
What was found
The abstract reports no raw numerical values or effect sizes. Total IGF-1 and IGFBP-3 serum concentrations increased significantly (p < 0.05) during exercise in participants without obesity but not in those with obesity, returning to baseline post-exercise. Growth hormone response was significantly higher in participants without obesity (p < 0.05). No significant exercise-induced changes were observed for free IGF-1 or IGFBP-1 in either group (p > 0.05).
Why it matters
This study shows that while obesity blunts total IGF-1 and growth hormone responses to acute endurance exercise, circulating levels of biologically active free IGF-1 are preserved due to a concurrent lack of increase in IGFBP-3.
Limits
The abstract omits sample size, participant demographics (sex, age), baseline clinical parameters, and all quantitative data (means, standard deviations, or effect sizes). Only a single acute bout of moderate cycling was evaluated, and downstream tissue-level signaling was not measured.
Cited by
- supports IGF-1 and thyroid hormones circulate bound to specific binding proteins in the body, meaning total circulating hormone levels can appear normal while free, biologically active hormone levels are significantly lower.