More fast food meals mean more excess weight

NEW YORK, Jan 17 (Reuters) A new study provides the best evidence to date that eating fast food makes you fat.

Among nearly 3,400 young adults participating in a long-term study, every additional fast food meal they consumed each week correlated with a substantial increase in body mass index (BMI), Dr Barry M Popkin of the University of North Carolina in Chapel Hill and colleagues found.

''It's a large effect,'' Popkin told Reuters Health in an interview. ''That's enough of an effect to take you from being non-diabetic to diabetic.'' Food eaten away from home now accounts for up to 42 percent of Americans' calorie intake, Popkin and his team note in their report in the American Journal of Clinical Nutrition. While the increase in restaurant and fast food consumption has occurred at the same time as the rise in obesity, they add, it's not clear if it's a contributing factor.

To separate out the effects of fast food meals and meals eaten in traditional restaurants, the researchers looked at 3,394 young adults participating in a heart disease study.

The investigators compared the study participants' consumption of fast foods and restaurant foods during year seven and year ten of the study with their BMIs at both time points.

BMI is a ratio of weight to height commonly used to determine if a person is underweight, normal weight, overweight, obese or morbidly obese.

The more fast food the subjects ate, the higher was their BMI, Popkin and colleagues found. For each additional fast food meal eaten per week during year seven, BMI increased by 0.13 points, while each additional fast food meal per week at year ten was tied to a 0.24 rise in BMI. This translates to 0.9 pounds and 1.7 pounds, respectively, for a person five foot ten inches tall.

People whose fast food intake rose between year seven and year ten showed a 0.20 increase in BMI.

However, the researchers found no association between meals eaten at traditional restaurants and increases in BMI; in fact, some analyses linked eating more often in restaurants to a slightly lower BMI.

The study confirms, Popkin said, that people who eat more fast food pack on more pounds. ''People have been trying to say that, but they didn't have the kind of evidence that we have now.'' REUTERS BDP KP0836