The prevalence of hidradenitis suppurativa (HS) has been estimated to be 1% of the population. Obesity is considered a co-morbidity, but the prevalence of HS in obese population is not known. A retrospective questionnaire was distributed to 383 patients over 2 years after bariatric surgery. Data on pre- and post-surgery HS symptoms and disease severity were studied. Disease severity was assessed by number of involved sites. General skin problems rated numerically on an anchored 1-10 scale. Valid responses were obtained from 249/383 (65%). A point prevalence of 18.1% (45/249) HS was found. The number of patients reporting HS symptoms after weight loss decreased by 35% and the mean number of involved sites was reduced from 1.93 to 1.22 following weight loss (p = 0.003). The prevalence of HS appears higher in the obese than in the background population, and a weight loss of more than 15% is associated with a significant reduction of disease severity.