At least half a dozen studies in the past have found that children gain weight at a faster rate during the summer holiday months than during the months they attend school. This phenomenon has been attributed to changes in diet and activity patterns during summer months when children are at home and tend to spend more time in front of screens and consume more unhealthy snacks and sugary beverages.  But a new study that followed changes in mass and height in 3,588 primary school children for five...