Clinical and Epidemiological Changes in French Soldiers After Deployment: Impact of Doxycycline Malaria Prophylaxis on Body Weight

Background Antibiotics are growth promotors used in animal farming. Doxycycline (DOXY) is a tetracycline antibiotic taken daily and continued 1 month after return to protect against malaria during travel and deployment in endemic areas. We evaluated DOXY impact on body weight in military international travelers. Materiel and methods A prospective cohort analysis was conducted in 2016-2018, recruiting 170 French soldiers before a 4-month assignment overseas. Many clinical data including anthropometric measures by an investigator were collected before and after deployment. Weight gain was defined by an increase of 2% from baseline. The study protocol was supported by the French Armed Forces Health Services and approved by the French ethics committee (IRB no. 2015-A01961-48, ref promoter 2015RC0). Written, informed consent was obtained with signature from each volunteer before inclusion. Results After deployment, 84 soldiers were followed up. Overall, 38/84 (45%) were deployed to Mali with DOXY malaria prophylaxis, and others were deployed to Iraq or Lebanon without malaria prophylaxis according to international recommendations. Body weight increased in 24/84 (30%), of whom 14/24 (58%) were exposed to DOXY. In bivariate analysis, DOXY had a positive but not significant effect on weight gain (P-value = .4). In the final logistic regression model (Fig. 3), weight gain after deployment positively correlated with an increase in waist circumference (odds ratio [OR] 1.23 with 95% CI [1.06-1.47]) suggesting fat gain; with sedentary work (OR 5.34; 95% CI [1.07-31.90]); and with probiotic intake (OR 5.27; 95% CI [1.51-20.40]). Weight impact of probiotics was more important when associated with DOXY intake (OR 6.86; 95% CI [1.52-38.1]; P-value = .016). Conclusions Doxycycline (DOXY) malaria prophylaxis during several months did not cause significant weight gain in soldiers. Further studies are required in older and less sportive traveling populations, and to investigate a cumulative effect over time and recurrent DOXY exposure. Doxycycline (DOXY) may enhance other growth-promoting factors including fatty food, sedentariness, and strain-specific probiotics contained in fermented dairy products which are also used as growth promotors.