The influence of fasting and energy restricting diets on IGF-1 levels in humans: A systematic review and meta-analysis

Ageing Res Rev. 2019 Aug:53:100910. doi: 10.1016/j.arr.2019.100910. Epub 2019 May 19.


Background: Fasting and energy restricting diets have a potential means of delaying or preventing the onset of a range of age-related metabolic and neoplastic diseases. Consistently at the centre of this effect appears to be a significant reduction in circulating IGF-1 levels. The aim of the current systematic review and meta-analysis was to determine the influence of fasting and energy restriction on IGF-1 levels in human subjects.

Methods: A comprehensive systematic search was conducted from onset of the database to February 2019 in Embase, MEDLINE/PubMed, and SCOPUS to identify randomized clinical trials that investigating the impact of fasting or energy restriction circulating IGF-1 levels. Effect size was reported as weighted mean difference (WMD) and 95% confidence intervals (CI) using a random-effects models. Subgroup analysis was performed to identify the probable source of heterogeneity among trials.

Results: Total pooling of fasting and energy restriction randomised controlled trials in WMD analysis revealed no significant effect on circulating IGF-1 levels (WMD: -16.41 ng/ml, 95% CI: -35.88, 3.07). Sub grouped analysis fasting regimens appeared to substantially reduce IGF-1 (WMD: -28.87 ng/ml, 95% CI: -43.69, -14.05, I2 = 00%), energy restricting regimens failed to do the same (WMD: -10.98 ng/ml, 95% CI: -33.08, 11.11, I2 = 90%). Within this final subgrouping, it was observed that only energy restriction regimens of 50% or greater of normal daily energy intake were capable of significantly reducing IGF-1 levels (WMD: -36.57 ng/ml, 95% CI: -59.19, -13.95, I2 = 00%). Finally, a meta regression were noted in which the percentage restriction of daily energy intake inversely correlated with plasma IGF-1 levels (p = 0.04).

Conclusion: This study uncovered that fasting significantly reduced levels of IGF-1, while energy restriction diets were successful only when intake was reduced by 50% or more.

Keywords: Energy restriction; Fasting; IGF-1.

Publication types

  • Meta-Analysis
  • Systematic Review

MeSH terms

  • Adult
  • Diet, Reducing
  • Fasting / blood*
  • Female
  • Humans
  • Insulin-Like Growth Factor I / analysis*
  • Male
  • Middle Aged
  • Young Adult


  • IGF1 protein, human
  • Insulin-Like Growth Factor I