We define overweight using a BMI criteria ( weight in kilograms divided by height in meters squared) as 25 to < 30 and obesity as a BMI of > or equal to 30. We have paid much attention to the growing obesity epidemic both in the United States and Canada.

In this week's Archives of Internal Medicine is an original study looking al alcohol consumption - how much alcohol we drink- as a risk factor for weight gain and the risk of becoming overweight in middle aged and older women. With more than half of adults consuming alcohol, it remains a calorie rich but nutrient poor source. For every gram of alcohol consumed, that translates to 7.1 kcal. For example, 4 ounces of wine has 10.8 grams translating to just under 80 calories. One 12-ounce beer is just shy of 95 calories.

The authors, out of Harvard University, looked at a long-term study with 12.9 years of follow up on the risk of weight gain and alcohol consumption. In the study, 19,220 women with a BMI from 18.5 to <25 were studied. Among these women, roughly 38% did not drink alcohol at all and 3% consumed 30 g/day or more. Compared with non-drinkers, women who consumed a greater amount of alcohol were significantly older, more likely to be white, current smokers, postmenopausal, hypertensive and had a slightly lower BMI when they entered the study. While it is clear that total calories increased with increasing alcohol, if the alcohol calories were removed from calculations, energy intake decreased in the group with the higher alcohol intake.

Alcohol intake was also positively associated with intake of red meats, poultry and high fat dairy products but inversely associated with intake of whole grains, refined grains, carbohydrates and fibre. Those women who consumed intermediate amounts of alcohol had the highest exercise and physical activity.

As these women were followed over the 12.9 years, on average, women gained weight progressively, but the weight gain was the largest for women who did not consume alcohol (3.63 kg) and then decreased with increasing alcohol intake. This association with increasing alcohol intake and reduction in weight gain was seen for all the 4 types of alcohol beverages with the strongest association found for red wine.

Previous studies have shown that this does not hold true for male drinkers. Male drinkers tend to add alcohol to their daily dietary intake whereas women drinkers usually substitute alcohol for other foods without increasing total energy intake. This did hold true in this study as well.

As well, there may be sex differences in how alcohol is metabolized. The pathway the body uses to metabolize alcohol differs in women from men and is a pathway that has low efficiency energy use.

Although it is true that heavier drinkers had a different profile with respect to diet, smoking and exercise, even when these factors were controlled for, the associations still persisted, which may mean that alcohol on its own has an effect on body weight.

In the study, only 3% were heavy drinkers (more than 2-3 drinks per day) and were noted to be more likely to be smokers (at least one third) and these heavy drinkers may have completely different lifestyle patterns than moderate drinkers. Because of the smaller numbers, the study cannot comment on this group.

While an interesting study, it should be remembered that alcohol consumption is a significant risk factor for disease and clearly, the risk versus benefit ratio is an individual consideration. Consuming 2 drinks per day of alcohol is associated with an increase risk of many cancers. Data shows that in a group of drinkers with this kind of consumption,  27 additional cases of breast cancer per 1000 women is projected.

Alcohol consumption has been linked to hypertension, whereas moderate alcohol intake offers long-term cognitive protection and reduces the risk of dementia in older adults according to some studies, and has also been shown to reduce the risk of heart disease.

The study does not imply alcohol consumption is endorsed, but reminds us that a complete alcohol intake review with your doctor is an important part of your physical evaluation. have the discussion about your intake and its potential risks as well as benefits.

WATCH: My segment on Canada AM this week: Alcohol and weight gain