The study was conducted by the Medical Corps of the Israel Defense Forces. Researchers pulled medical data from the youths reporting for obligatory military duty between 2002 and 2015. The study included 299,163 (49.9%) young men and 301,241 (50.1%) young women, of whom 56,007 (18.7%) and 49,054 (16.3%) were diagnosed with acne, respectively. Acne diagnoses were made by dermatologists and likely only encompassed moderate-severe cases; data on individuals with mild cases of acne, therefore, was not available.
The researchers used BMI grouping established by the World Health Organization: <18.5 (underweight), 18.5-21.99 (reference group), 22-24.99, 25-27.49 (overweight), 27.5-29.99, 30-32.49 (obese), 32.5-34.9, and ≥35 (severely obese).
The incidence of acne among men decreased from 19.9% in the underweight group to 13.9% in the severely obese group. The incidence of acne among the women decreased from 16.9% in the low-normal group to 11.3% in the severely obese group. For every 1-unit increase in BMI, the adjusted odds of acne decreased by 3.2% (95% CI, 2.9%-3.5%) among men and 2.6% (95% CI, 2.3%-3%) among women.
Although these data represent a nationwide, cross-sectional study, data from some individuals were excluded. Individuals with extreme BMI values would have been excluded from military service, therefore, their data would not be recorded for this study. The researchers further excluded data from soldiers serving more or less time than is typical for compulsory military service.
The researchers were unable to account for potential confounders such as previous acne treatment, contraceptive use, and diet. They did not gather data on the incidence of polycystic ovary syndrome among the women, which is notable, as this condition is associated with both acne and obesity and affects 4% to 18% of reproductive-age women. In addition, no discernment was made in the severity of acne cases, nor was there evidence of consideration of other skin disorders.
Although previous studies on this subject have yielded conflicting results, this report makes a clear inverse correlation between BMI levels and the odds of having acne. The researchers made no inferences of a causational relationship between the two but suggested that excessive adipose tissue in individuals with higher BMIs may have a protective effect against acne.
Snast I, Dalal A, Twig G, et al. Acne and obesity: a nationwide study of 600,404 adolescents [published online April 9, 2019]. J Am Acad of Dermatol. doi:doi.org/10.1016/j.jaad.2019.04.009
This article originally appeared on Dermatology Advisor