INS and cancer: Most adolescents are inactive1 and this inactivity tracks into adulthood34 increasing risk of diabetes, cancer and mortality.56 Over 10 min/day of physical activity every year is replaced by sedentary time between 9 and 10, and 13 and 14 years-old;1 a 10 min increase in moderate to vigorous physical activity (MVPA) was associated with a smaller waist circumference and lower fasting insulin among young people in a large worldwide meta-analysis.26 Pubertal, brain and social development during adolescence leads to new capacity for health behaviours7 increasing the likelihood of long-term change.