In new research that offers new clues to the connection between obesity and gut bacteria, scientists have discovered that individuals on long-term antibiotic treatments are more likely to gain weight.
 

The study, published in the journal Antimicrobial Agents and Chemotherapy, suggests antibiotics may significantly alter the makeup and balance of intestinal bacteria, which past research has linked to obesity and diabetes.
 

The findings, by Didier Raoult of Aix-Marseille University in France, are based on a review of 48 patients who were being treated long-term with doxycycline and hydroxychloroquine for a bacterial infection known as "Q fever." Nearly one quarter of the treated patients gained five to 30 pounds more than expected over an 18-month period.
 

"Doxycycline and hydroxychloroquine treatment exhibited a reproducible effect on the community structure of the gastrointestinal microbiota, with treated patients presenting significantly lower concentrations of beneficial bacteria, Bacteroidetes, Firmicutes, and Lactobacilli," said Angelakis Emmanouil, of Unite de Recherche sur les Maladies Infectieuses et Tropicales Emergentes (URMITE), CNRS, Marseille.
 

The findings suggest antibiotics may make some people more vulnerable to weight gain and highlight the need for reduced calorie diets for patients undergoing long-term treatment, the researchers said.