MONDAY, Nov. 19 (HealthDay News) -- Children who regularly attend daycare are more likely to be overweight than those who stay at home with a parent, but the reasons for this difference are unknown, according to a new study.

Canadian researchers looked at more than 1,600 families in Quebec with children born in 1997 or 1998. Mothers were interviewed about the care of their children at one and a half, two and a half, three and a half and four years of age.

"We found that children whose primary-care arrangement between one and a half and four years was in a daycare center or with an extended family member were around 50 percent more likely to be overweight or obese between the ages of 4 and 10 years compared to those cared for at home by their parents," study leader Dr. Marie-Claude Geoffroy said in a University of Montreal news release.

"This difference cannot be explained by known risk factors such as socioeconomic status of the parents, breastfeeding, body-mass index of the mother or employment status of the mother," she added. The study also uncovered only an association between daycare attendance and overweight, not a cause-and-effect relationship.

The study was published this month in the Journal of Pediatrics.

Diet and physical activity levels are among the areas that need to be examined in order to determine why children who go to daycare are more likely to gain weight, noted study co-director Dr. Sylvana Cote.

"Parents don't have to worry; however, I suggest to parents they ensure their children eat well and get enough physical activity, whether at home or at daycare," she said in the news release.

The researchers said daycare has the potential to reduce weight problems in children, through methods such as encouraging physical activity and healthy eating.

More information

The U.S. Department of Health and Human Services explains how to keep children at a healthy weight.