Psychological and behavioural risk factors for obesity onset in adolescence

Many factors have been implicated in the development of obesity during childhood. For example, dietary behaviours such as fast food intake and soft drink consumption are associated with weight gain and obesity onset. Likewise, hours of TV viewing, indicative of sedentary behaviour, are predictive of later obesity prevalence in some but not all studies. Overall, much of the evidence on risk factors for obesity in children comes from cross-sectional rather than prospective studies thereby limiting conclusions concerning causality. In addition, the picture is complicated by the difference in potency of some factors according to whether children are low or high socio-economic status, or from first world or economically developing countries.

Evidence on risk factors specific to obesity onset in adolescence is in relatively short supply. The prevalence of overweight and obesity is generally lower in adolescence than that earlier in childhood. Also, the proportion overweight may remain relatively stable during adolescence (Crimmins et al, 2007). In determining which children become overweight or obese adolescents, the most important risk appears to be parental obesity. In one Australian study, for example, children whose parents were overweight or obese were over 6 times more likely to change from having a normal BMI at 5 years old to being overweight at 14 (Mamun et al, 2005). While this suggests the influence of genetic factors, such family association also involves shared dietary and activity/sedentary patterns.

Perhaps the clearest evidence for a behaviour associated with obesity onset in adolescence comes from studies looking at teenage weight control attempts. Often designed with the aim to investigate the emergence of disordered eating, several prospective investigations have linked voluntary weight control with subsequent weight gain. Two of the more recent studies illustrate this relationship and some of the underlying reasoning. Stice et al (2005) followed a cohort of nearly 500 girls aged 11-15 years over a 4 year period. Self-reported dietary restraint and compensatory behaviours such as vomiting or laxative use predicted obesity onset, as did depressive symptoms and parental obesity. Neumark-Sztainer et al (2006) followed up a group of 2,500 adolescents 5 years after an initial evaluation. In this sample, compared with adolescents not using any weight control behaviours, those attempting weight control at Time 1 were at 3 times greater risk of overweight 5 years later. It is of note that this risk applied equally to weight control attempts by girls and boys. In addition, for girls at least, weight gain was associated with the use of either healthy or extreme/unhealthy weight control behaviours. Any attempt at weight control apparently resulted in long term failure, and for some, obesity onset.
How should these results be interpreted? One suggestion has been that dieting leads to an increase in metabolic efficiency leading dieters to require less food energy to maintain weight (Field et al, 2003). Alternatively, adolescent dieting may lead to a cycle of restriction followed by binge eating and an eventual dysregulation of appetite control. Certainly, the meaning of dieting for adolescents may be quite different to the reduced energy diets used in the management of adult obesity. Much of adolescent dieting may be intentional and temporary rather than organised and long-term.

A further possibility is that the obesity onset associated with voluntary weight control simply identifies a proportion of adolescents who are at high risk of obesity. Overweight adolescents are more likely to have obese parents and dieting behaviour is more common in those with higher BMI. Moreover, body weight and shape concern is associated with depression and adolescent depression is itself a risk for obesity onset. For many adolescents, self-reported weight control may be a proxy for a tendency to over-consumption and weight gain. It is not dieting that makes people fat but being (and feeling) fat that makes them try to diet (Hill, 2004). While evidence is accumulating that adolescent obesity can be managed, the successful programmes are intensive and long-lasting. The research described above suggests the need for more community-based weight management resources to help adolescents who are trying, and broadly failing, to manage their increasing weight.

References

1. Crimmins, NA, Dolan, LM, Martin, LJ, Bean, JA, Daniels, SR, Lawson, ML, Goodman, E & Woo, JG. Stability of adolescent body mass index during three years of follow-up. Journal of Pediatrics, 151, 383-387, 2007.

2. Field, AE, Austin, SB, Taylor, CB, Malspeis, S, Rosner, B, Rockett, HR, Gillman, MW & Colditz, GA. Relation between dieting and weight change among preadolescents and adolescents. Pediatrics, 112, 900-906, 2003.

3. Hill, AJ. Does dieting make you fat? British Journal of Nutrition, 92, S15-S18, 2004

4. Mamun, AA, Lawlor, DA, O’Callaghan, MJ, Williams, GM & Najman, JM. Family and early life factors associated with changes in overweight status between 5 and 14 years: findings from the Mater University Study of Pregnancy and its outcomes. International Journal of Obesity, 29, 475-482, 2005.

5. Neumark-Sztainer, D, Wall, M, Guo, J, Story, M, Haines, J & Eisenberg, M. Obesity, disordered eating and eating disorders in a longitudinal study of adolescents: how do dieters fare 5 years later? Journal of the American Dietetic Association, 106, 559-568, 2006.

6. Stice, E, Presnell, K, Shaw, H & Rohde, P. Psychological and behavioural risk factors for obesity onset in adolescent girls: a prospective study. Journal of Counselling and Clinical Psychology, 73, 195-202, 2005.