Physical activity: Timing is everything



Children who exercise vigorously for 30 minutes before lunch consume 10% fewer calories and 25% less fat than when they eat following a reading period.

Exercise is great. But exercise at the right time is even better! Setting her sights on preventing childhood obesity through physical activity, Marie-Ève Mathieu, researcher at the CHU Sainte-Justine Research Centre and professor in the Department of Kinesiology at Université de Montréal, ascertained that children who exercise vigorously for 30 minutes before lunch consume 10% fewer calories and 25% less fat than when they eat following a reading period.

Her findings confirm that physical activity must be approached as a treatment, with the right dose at the right time for maximum benefit. To determine the dosage, Marie-Ève Mathieu analyzed epidemiological data from a cohort of 600 families over a decade. She also monitored young people ages 15 to 25 in the lab and recently carried out tests in preschool children. She compared a number of exercise scenarios of varying intensities before and after the students' lunch period. Her initial results point to the fact that engaging in physical activity right before the midday break appears to lead to a calorie deficit (fewer calories ingested) for the entire day.

Should recess be held before lunch? The jury is still out, since Marie-Ève Mathieu has yet to determine whether the time is best for overweight children and those suffering from a chronic illness. Indeed, a number of studies have shown that diabetic patients should exercise after meals to lower their blood sugar, while people with high blood pressure benefit more when they get moving in the evening. Several schools have expressed their interest in taking part in the various projects she is currently leading.