Interrelations of Leptin and Interleukin-6 in Vitamin D Deficient and Overweight Orthodox Nuns from Northern Greece: A Pilot Study

<b>Background/Objectives:</b> Athonian fasting, a rigorous form of intermittent fasting practiced by Christian Orthodox nuns and a subset of the Mediterranean diet, has known health benefits, but its impact on the interplay of adipokines, inflammatory cytokines, and vitamin D status remains under-investigated. This study aimed to elucidate these relationships within this controlled dietary context. <b>Methods:</b> This cross-sectional study examined the interplay of leptin, interleukin-6 (IL-6), and vitamin D in 41 overweight, vitamin D-sufficient Christian Orthodox nuns practicing Athonian fasting. Anthropometric, biochemical, and inflammatory markers were assessed in the nuns (mean age 53.4 ± 17.1 years, median monastery stay 17 years, median BMI 26.8 kg/m²). <b>Results:</b> Analysis revealed significant positive correlations between age and monastery stay (r = 0.615, <i>p</i> < 0.001), age and visceral fat (ρ = 0.791, <i>p</i> < 0.001), age and IL-6 (ρ = 0.647, <i>p</i> < 0.001), and BMI and IL-6 (ρ = 0.622, <i>p</i> < 0.001). Strong associations existed between adiposity (BMI, body fat, visceral fat), leptin, and IL-6. Specifically, body fat showed substantial positive correlations with visceral fat (ρ = 0.858, <i>p</i> < 0.001), leptin (ρ = 0.538, <i>p</i> < 0.001), and IL-6 (ρ = 0.675, <i>p</i> < 0.001). Visceral fat demonstrated strong positive correlations with leptin (ρ = 0.613, <i>p</i> < 0.001) and IL-6 (ρ = 0.741, <i>p</i> < 0.001). A significant positive correlation was also observed between leptin and IL-6 (ρ = 0.507, <i>p</i> = 0.003). Conversely, a significant negative correlation was found between 25(OH)D and PTH (ρ = -0.380, <i>p</i> = 0.016). Multivariate regression analysis did not reveal independent effects of leptin or IL-6 after adjusting for other factors. <b>Conclusions:</b> This study reveals a complex interplay of adiposity, inflammation, and vitamin D status in this unique population of Orthodox monastery fasters. The strong correlations suggest potential targets for interventions aimed at improving metabolic health. Future research should investigate the effects of vitamin D within the context of Athonian fasting.