The comparative long-term effects of surgical and medical weight-loss treatments on rates of infections are sparsely explored. We compared the use of antibiotics as a proxy for infectious disease in patients with severe obesity undergoing surgical (ST) or medical treatment (MT), and with the general population.


Data from patients referred to a tertiary care center from 2005-10 were linked to follow-up data retrieved from the national Norwegian Prescription Database from 2005-15. All prescriptions collected by Norwegian citizens are registered and the coverage is almost complete. Yearly user rate of antibiotics (ATC-code J01) in the ST and MT groups were compared using mixed models for repeated measures with binary outcomes. In addition, age, gender and time-period weighted rates were constructed using rates from the general population (Statistics Norway, SSB).


A total of 1995 consecutive patients (67% women), mean (SD) age 43.2 (12.2) years, BMI 44.2 (6.0) kg/m2, were included, and 47% underwent bariatric surgery (92% gastric bypass). The MT and ST groups were followed for median (range) 7.2 (5.3-10.0) years and 5.8 (2.1-9.1) years. There was a small but significantly higher risk for use of antibiotics in the MT group compared to the ST group during follow up (RR 1.06 (95% CI 1.02-1.11), Risk Difference 0.02% (95% CI 0.00-0.04)). The age, gender and time-period weighted rates for the general population were almost unchanged for the whole follow up at around 30%. However, the rates for the patients with severe obesity ranged from 42% to 55% over the duration of follow up.


Patients with severe obesity use almost twice as much antibiotics compared with age- and gender- matched rates from the general population of Norway, and the use of antibiotics does not decline after either medical or surgical treatment for obesity.