Mary Vallis National Post, with files from Reuters Frequent marijuana users devour up to 40% more calories than their peers but are no more likely be be fat, a new study suggests. Americans aged 20 to 59 who smoked marijuana at least once a month indulged in more beer, liquor, potato chips, cheese and pork than non-users, researchers report in the journal Public Health Nutrition today. The marijuana smokers also ate fewer fresh fruits or vegetables and smoked nearly three times as many tobacco cigarettes as non-users. But the study found their habits were not a detriment to their nutritional health. The marijuana users showed normal levels of vitamins and minerals in spite of their vices, and slightly lower body mass indexes than their peers. (Body mass index compares a person's weight to their height to gauge obesity). "That is the surprising finding," said Dr. Ellen Smit, lead author of the study and a professor of medicine at the University at Buffalo. One explanation is that smoking marijuana is thought to increase a person's metabolic rate.