At the recent Food in Action conference organised in conjunction with EUFIC, psychologist Dr Andrew Hill revealed a number of counter-intuitive findings about what makes adolescents obese. His findings shine an alternative light on the issue and offer insight into new approaches to tackle this problem.
There are now a number of studies which have followed a large group of children through adolescence over time. This makes it possible to examine what behaviors contribute to subsequent obesity. Two such studies, the 1970 British Birth Cohort, and the US based EAT (Eating Among Teens) and others like them, have discovered a risk factor for obesity that is not only surprising, but the opposite of what you might expect – dieting.1,2
Dieters more likely to develop obesity
Viner and Cole found that adolescents who were dieting to lose weight at age 16 were significantly more likely to be obese at age 30 than non-dieters.1 Neumark-Sztainer and colleagues found that teenagers who reported to be dieting at the onset of the study period were three times more likely to be obese after five years than their non-dieting peers.2 These findings are equally true for boys and girls.
Type of diet makes no difference
The Neumark-Sztainer study also examined whether the type of diets the adolescents followed made any difference. Dr Hill highlighted that ‘healthy’ practices like the low-fat, well-balanced diets rich in fruit and vegetables (i.e. the type that health professionals would recommend) were as unsuccessful as ‘unhealthy’ weight loss behaviour such as fasting, missing meals, extreme and faddy diets or self induced vomiting.
Does dieting lead to weight gain?
There are various possibilities as to why dieting may lead to obesity such as the deregulation of appetite, where hunger becomes dissociated from actual eating, and dietary restraint, i.e. not eating to appetite/satiation, which can lead to binge eating. Both of these factors leave the dieter vulnerable to overeating and hence weight gain. However, whatever happens once the child starts dieting Dr Hill points out:
‘Dieting in adolescence is a proxy for difficulty in regulating food intake. These teenagers have recognised they have a weight problem, responded by dieting, and broadly failed. Thus, dieting is not the cause but a response to being overweight’
Family influence
So why are these children struggling with their weight? Dr Hill explained that the literature consistently reveals that the most powerful risk factor for weight problems in children and young adults is having overweight or obese parents. For example, the Health Survey for England (2006) shows how the risk of obesity in children aged 2-15 years jumps sharply from almost zero to about 15% if one, and up to 28% if both parents are overweight or obese.3 Most likely, genetic and environmental factors combine to bring about this increased risk.
Other risk factors
A recent study by Stice and colleagues recorded psychological profiles and behavioural practices in a group of 500 adolescent girls and followed them for four years.4 It was found that dietary restraint, radical weight control practices, like vomiting and appetite suppressants, depressive symptoms and perceived parental obesity (but not high-fat food consumption or exercise frequency) predicted the onset of obesity. Apart from parental obesity and dieting practices, this study also highlights a link between depression and obesity.
‘There is now a substantial body of evidence linking depression with the development of obesity’ added Dr Hill. ‘Some studies have tried to unravel the underlying causes. Body dissatisfaction, perceived social isolation, the shame of being overweight and being teased and bullied seem to be important mediators.’
The way forward
The evidence clearly shows that the development of obesity in young people is not simply about physical activity and energy intake. It is undoubtedly a complex problem where there are a lot of (poorly understood) psychological vulnerabilities involved. So what is the way forward? Dr Hill suggests:
‘Creating a public health environment encouraging weight control is not enough for our young people. We need tailored interventions, and if we target anyone it should be families where both parents are obese or overweight. We need people on the ground who can provide individual assistance to help these families overcome the barriers to their long term success in weight control.’
References
- Viner RM and Cole TJ (2006). Who changes body mass between adolescence and adulthood? Factors predicting change in BMI between 16 years and 30 years in the 1970 British Birth Cohort. International Journal of Obesity 30:1368-1374
- Neumark-Sztainer DR , Wall MM, Haines JI et al (2007). Shared risk and protective factors for overweight and disordered eating in adolescents. American Journal of Preventive Medicine 33:359-369
- Health Survey for England 2006: CVD and risk factors adults, obesity and risk factors children (2008). Available at http://www.ic.nhs.uk/statistics-and-data-collections/healthand-lifestyles-related-surveys/health-survey-for-england/health-survey-for-england-2006:-cvd-and-risk-factors-adults-obesity-and-risk-factors-children
- Stice E, Presnell K, Shaw H and Rohde P (2005). Psychological and behavioural risk factors for obesity onset in adolescent girls: a prospective study. Journal of Consultant Clinical Psychology 73:195-202
Conference proceedings available at: http://www.focusbiz.co.uk/conferences/foodinaction/day2.htm
