Programmes to prevent childhood overweight and obesity, which focus on modification of dietary behaviour, increasing physical activity or reducing sedentary behaviour, have been underway for a number of years in countries all over the world. Encouraging results have provided useful data for the development of future initiatives. This is the second in a series of articles discussing current research on the prevention of childhood obesity. The Diet
Any obesity prevention programme that targets the general child population cannot
have a dietary regimen that specifically aims to reduce calorie intake, as this might cause unwanted weight loss in non-overweight children.
Ideally any public health programme would aim to decrease both over and underweight in children, thus studies have looked to improve the general ‘healthiness’ of the diet for example by reducing fat intake (1), increasing portions of fruit and vegetables (2) or reducing the consumption of carbonated drinks (3). Physical activity at school
The demands of modern school curricula make it difficult to include any additional physical activity as there are fears this may have a negative impact on academic performance. However an Australian primary school study which introduced 1¼ hours of fitness training each day found no loss of academic ability (assessed by arithmetic and reading tests) despite 40-60 minutes less formal teaching per day (4). The study reported improved physical work capacity and significant decreases in body fat compared to children following the usual physical education programme. This programme has since been adopted by 60% of primary schools in the state of South Australia. Nothing similar has yet been measured in secondary schools where the pressure to succeed at exams is intense.Physical activity at leisure
Leisure activities are also important especially for older children who are starting to make choices about how they spend their free time. The ongoing French ICAPS study (5) has an emphasis on increasing the recreational and daily-life physical activity of adolescents. Classroom debates and educational activities were used, in the intervention group, to develop positive attitudes towards exercise, and taster sessions of attractive activities were offered during break times and after school. Practical support came from extending the school bus service (flexible timing) and adapting times and places for activities. The emphasis was on having fun, being sociable and making friends in a non-competitive environment. After six months of intervention the proportion of both boys and girls engaged in leisure physical activities was significantly increased in the intervention group, whereas it was unchanged among control children. After 2 years they were 20% less overweight children in the group "action " versus the group " control". Other studies have incorporated a similar approach of classroom education and community support to encourage adolescents to be more active in their daily lives (2). Sedentary behaviour
Some of the most successful studies have worked on reducing the number of hours spent being sedentary. A small study in the US provided 8 and 9 year old children in one school with an 18 lesson, 6 month classroom curriculum focused on reducing television viewing and computer games (6). Compared with a matched control school, children receiving the intervention had lower average body mass index (a measure of weight relative to height) and skinfold thickness. Parents also reported decreases in children’s television viewing. No studies in older children have focused solely on reducing TV viewing but the ‘Planet Health’ study in the US (2) found that TV viewing and obesity were clearly linked in adolescent girls (but not boys), and that for each hour reduction in TV watching there was a 15% reduction in the risk of obesity. The ICAPS study mentioned above (5) has reported a reduction in the number of adolescents watching more than 3 hours of TV/day, but again with greater success amongst girls than boys.