Acne and obesity: A nationwide study of 600,404 adolescents

Background: The association between body mass index (BMI) and acne is unclear. Objective: To determine the association between BMI and acne in youths. Methods: A nationwide, population-based, cross-sectional study was conducted in 2002-2015 by using medical data on 600,404 youths during compulsory military service. BMI was measured at age 17 years. Acne was diagnosed by dermatologists. Unadjusted and adjusted odds ratios (aORs) of acne in relation to BMI (stratified into 8 groups) were calculated, with the low-normal group (18.5≤ BMI ≤21.99 kg/m²) serving as the reference. Results: The study included 299,163 males (49.9%) and 301,241 females (50.1%) with a mean age of 18.9 years (standard deviation, 0.6) and 18.7 years (standard deviation, 0.5), respectively, at recruitment. Acne was diagnosed in 55,842 males (18.7%) and 48,969 females (16.3%). The proportion of participants with acne decreased gradually from the underweight to the severely obese group (males, from 19.9% to 13.9%; females, from 16.9% to 11.3%). The findings on multivariable analysis were similar to the unadjusted analysis results, showing the lowest odds of acne in severely obese participants (aOR for males, 0.53; 95% confidence interval, 0.42-0.64; aOR for females, 0.5; 95% confidence interval, 0.37-0.62). The findings persisted in the sensitivity analyses. Limitations: Information was lacking on potential confounders and acne severity. Conclusion: In youths, overweight and obesity are inversely associated with acne in a dose-dependent manner.