Why Diets Fail

Eating Behaviours – Influences on Eating Behaviour

In this course, Dr Laura Renshaw-Vuillier (Bournemouth University) explores influences on eating behaviours. In the first lecture, we think about some biological and psychological explanations for the failure of dieting, as well as some suggestions for how to overcome these. In the second lecture, we think about whether role models and celebrity media exposure can be attributed to the prevalence of anorexia nervosa. Next, we review the methodology and results of Scott-Van Zeeland and colleagues’ 2014 paper, which explored specific genes which could be attributed to anorexia nervosa. In the fourth and final lecture, we review the methodology and results of Guardia and colleagues’ 2012 paper, which looked at the self-perception of physical body size in individuals with anorexia nervosa.

Why Diets Fail

In this lecture, we think about some of the successes and failures in dieting, focusing in particular on: (i) the fact that around 80-90% of people who lose weight will regain some of it in a year, with a proportion gaining more weight than they lost originally; (ii) three key mechanisms for why diets fail being their strict and unsustainable rules, the need to keep reducing calorific intake to continue losing weight, and the body’s changing responses to the ghrelin and leptin hormones; (iii) the ironic process as a psychological explanation for the failure of dieting, which posits that dieting puts eating at the forefront of the mind, making it a bigger part of everyday thoughts than when not dieting; (iv) Daniel Wegner’s ‘white bear experiment’ as an example of this psychological effect; (v) the series of connected events which make up the sparrow model; (vi) the restraint eating theory, which states that ignoring internal cues for hunger/satiation uses up cognitive resources; (vii) disinhibition theory, which states that minor deviations from the diet can lead to binging; (viii) the boundary model, which states that individuals undertaking dieting have smaller boundaries of hunger and fullness, which can lead to increased eating; (ix) some suggestions for how to overcome failed diets including by focusing on maintaining, rather than losing, weight and eating a balanced diet, rather than thinking of food as good or bad; (x) orthorexia nervosa, a condition which manifests as an obsession with healthy eating.