It isn't just the beer that contributes to beer bellies. It could also be the extra calories, fat and unhealthy eating choices that may come with moderate drinking.

A recent study found that men consume an additional 433 calories (equivalent to a McDonald's double cheeseburger) on days they drink a moderateamount of alcohol. About 61% of the caloric increase comes from the alcohol itself. Men also report eating higher amounts of saturated fats and meat, and less fruit and milk, on those days than on days when they aren't drinking, the study showed.

Women fared a bit better, taking in an extra 300 calories on moderate-drinking days, from the alcohol and eating fattier foods. But women's increase in calories from additional eating wasn't statistically significant, the study said.

'Men and women ate less healthily on days they drank alcohol,' said Rosalind Breslow, an epidemiologist with the federal National Institute on Alcohol Abuse and Alcoholism and lead author of the study. 'Poorer food choices on drinking days have public-health implications,' she said.

The findings dovetail with controlled lab studies in which participants generally eat more food after consuming alcohol. Researchers suggest that alcohol may enhance 'the short-term rewarding effects' of consuming food, according to a 2010 report in the journal Physiology & Behavior that reviewed previous studies on alcohol, appetite and obesity.

But other studies have pointed to a different trend. Moderate drinkers gain less weight over time than either heavy drinkers or people who abstain from alcohol, particularly women, this research has shown. Moderate drinking is considered having about two drinks a day for men and one for women.

'People who gain the least weight are moderate drinkers, regardless of [alcoholic] beverage choice,' said Eric Rimm, an associate professor of epidemiology and nutrition at Harvard Medical School and chairman of the 2010 review of alcohol in the federal dietary guidelines. The weight-gain difference is modest, and 'starting to drink is not a weight-loss diet,' he said.

The various research efforts form part of a long-standing debate about how alcohol affects people's appetites, weight and overall health. Researchers say there aren't simple answers, and suggest that individuals' metabolism, drinking patterns and gender may play a role.

Alcohol is 'a real wild card when it comes to weight management,' said Karen Miller-Kovach, chief scientific officer of Weight Watchers International. At seven calories per gram, alcohol is closer to fat than to carbohydrate or protein in caloric content, she said. Alcohol tends to lower restraint, she notes, causing a person to become more indulgent with what they're eating.

Research bolstering the role of moderate drinking in helping to control weight gain was published in 2004 in the journal Obesity Research. That study followed nearly 50,000 women over eight years. An earlier study, published in the American Journal of Epidemiology in 1994, followed more than 7,000 people for 10 years and found that moderate drinkers gained less weight than nondrinkers. Studies comparing changes in waist circumference among different groups have yielded similar results.

Dr. Rimm said it isn't clear why moderate drinking may be protective against typical weight gain, but it could have to do with metabolic adjustments. After people drink alcohol, their heart rate increases so they burn more calories in the following hour.

'It's a modest amount,' he said. 'But if you take an individual that eats 100 calories instead of a glass of wine, the person drinking the glass of wine will have a slight increase in the amount of calories burned.'

Food choices could also play a role. Some studies suggest that women who drink alcohol eat fewer sweet foods, possibly because alcohol stimulates the same pleasure center in the brain as sweets, said Dr. Rimm. That isn't seen as consistently in men.

Men have more of the alcohol dehydrogenase group of enzymes that metabolize some alcohol in the stomach than women, said Andrea N. Giancoli, spokeswoman for the Academy of Nutrition and Dietetics, a professional organization.

One theory for what this might mean is that women's bodies divertalcohol not being broken down in the stomach to a different metabolic pathway that results in more calories being burned, said Ms. Giancoli, a registered dietitian near Los Angeles. As a result, fewer calories from alcohol may be stored in women as fat, she said.

Another factor is drinking patterns. A 2005 study in the American Journal of Epidemiology looked at data from 45,896 drinkers. It found that as the quantity of drinking increased from one to four drinks in a day, the subjects' body-mass index increased.

'People who drank the least often but drank more on the days that they drank had higher BMI,' said Dr. Breslow, who co-authored the study.

Dr. Breslow's latest study, which found caloric intake increases with moderate drinking, didn't look at associations between alcohol and body weight or track food choices and diets over time. She suggested that people who increase their caloric intake with moderate drinking one day might compensate the next day by consuming less.

The study, which appeared in the May issue of the American Journal of Clinical Nutrition, analyzed data from the National Health and Nutrition Examination Survey and included 1,864 mostlymoderate drinkers.

Another study, which looked at data from nearly 16,000 individuals over a year, concluded that as alcoholconsumption increased there was a decline in diet quality.

That research was published in the Journal of the American Dietetic Association in 2010.

David Jensen, a 56-year-old who considers himself overweight, says cutting his daily drink or two helped him reduce nighttime snacking. 'You have a glass of wine and then it's, oh man, I need cheese with that, or I need chocolate. You end up eating all this other stuff,' said Mr. Jensen, who lives near Seattle and works as a translator for financial clients.

Last year he stopped drinking for five months and lost just over 10 pounds 'with really no effort,' Mr. Jensen said.