People who have gastric bypass surgery to lose weight will likely get drunk faster, says a doctor who studied the effects of alcohol on surgery patients.

Dr. John Morton, a professor of surgery at Stanford University, said he was inspired to do the study following an episode of The Oprah Winfrey Show.

"After the Oprah show Suddenly Skinny aired in October 2006, I got question after question from patients asking, 'What happens when I drink alcohol?'" Morton recalled, noting he heard anecdotes of a patient who drank one glass of wine and was charged with impaired driving.

Gastric bypass or stomach stapling reduces the size of the stomach and bypasses part of the small intestine in people who are at least 100 pounds overweight and have unsuccessfully tried to lose weight through diet, increased physical activity and anti-obesity drugs.

By shrinking the size of the stomach, patients cannot eat as much.

Slower alcohol metabolism

The researchers measured the effects of alcohol on 19 people who had gastric bypass surgery at least one year before the experiment, and 17 control subjects who did not have the operation.

All participants were told to drink five ounces of red wine within 15 minutes and then had their breath alcohol measured every five minutes until levels dropped to zero.

Among gastric bypass patients, breath alcohol levels reached 0.08 per cent compared with 0.05 per cent in the controls. It also took longer for levels to return to zero for surgery patients, 108 minutes compared with 72 minutes in the controls.

Gastric bypass patients may not be aware of the risks of drinking they face because of a decrease in the enzyme alcohol dehydrogenase that helps metabolize alcohol, the researchers said.

Gastric emptying also increases when alcohol is consumed, which potentially allows patients to eat more food and gain weight, Morton cautioned.

The study will be published in the official journal of the American Society for Bariatric Surgery, and was presented at the society's conference this week in San Diego.

Other research presented at the conference suggested:

• Extremely obese people with depression or anxiety tend to lose less weight after obesity surgery than people who are mentally healthy.
• People who gain or lose about 10 pounds before gastric bypass surgery both showed a 60 to 70 per cent reduction in excess weight at 12 and 24 months after the operation. Patients are often advised to lose weight before the surgery.
• The complication rate for teens undergoing gastric bypass surgery may be half that of adults after 30 days, according to a study of more than 300 teens and 55,000 adults. The long-term effects remain unknown.

In Canada, most provincial health plans pay for the surgery but demand outstrips supply. About 4,500 people seek bariatric surgery each year, but fewer than 300 have the surgery in Canada.