The stomach bug H. pylori is responsible for most ulcers, but it can usually be eradicated with medication. However, many people who undergo this treatment put on weight - and now Japanese scientist think they know why.

Elimination of H. pylori infection leads to a significant increase in levels of the powerful appetite-stimulating hormone ghrelin in the tissues of the stomach where it is produced, the researchers report in the American Journal of Gastroenterology.

“This could lead to the increased appetite and weight gain seen following H. pylori eradication,” Dr. Atsushi Tatsuguchi and colleagues from Nippon Medical School Hospital in Tokyo write, noting that Obesity is “one of the counter-effects” of getting rid of the bacterium.

The investigators studied changes in ghrelin in gastric tissue from 61 patients infected with H. pylori and 22 healthy “controls.” Compared with the uninfected group, the patients with H. pylori had a significantly fewer ghrelin-producing cells.

After treatment, a standard breath test confirmed H. pylori had been cleared from the stomachs of 50 of the 61 infected patients.

The team saw a significant increase in the number of ghrelin-producing cells among participants who were successfully treated, but not in the 11 patients who did not respond to H. pylori eradication therapy.

Tatsuguchi and colleagues say that it is “reasonable to speculate” that increased ghrelin following H. pylori eradication “may stimulate nutritional parameters leading to obesity.”

SOURCE: American Journal of Gastroenterology, November 2004.