Introduction: Outcomes for individual participants who undergo any given weight loss treatment vary considerably (1, 2); some participants lose little or nothing while others achieve impressive losses. This project aims to identify any subject characteristics that predict successful weight loss on different types of weight loss programs.

Methods: The study is a randomised dietary intervention trial. Initial baseline testing was performed then 200 participants were randomised to:
A. Rapid Weight Loss (RWL) Group- participants were instructed bi-weekly by a dietitian to follow a VLCD over three months;
B. Gradual Weight Loss (GWL) Group- participants were instructed bi-weekly by a dietitian to lose weight gradually over a 9-month period.

Participants were deemed successful if they lost 15% of their body weight.

Results: In the GWL group, baseline hunger level was positively related to weight loss success (p<0.05). Seeking social support was also related to weight loss success in the GWL group; each additional point on the Ways of Coping Checklist- Revised subscale ‘Seeks Social Support’ increased the odds of weight loss success by 270%(p<0.05). In the RWL group, being less preoccupied with food at baseline was related to weight loss success; such that each additional centimetre placed on the VAS following the question ‘How much are you preoccupied by thoughts of food?’ was associated with a 32% reduction in the odds of weight loss success (p<0.05). The personality trait ‘agreeableness’ was positively associated with weight loss success on the RWL program(p<0.05).

Conclusion: Agreeable obese individuals who are less preoccupied with food are more successful at losing weight rapidly than individuals who are less agreeable and more preoccupied with food. In contrast, individuals who are hungrier and seek social support when needed are more likely to be successful at losing weight gradually than those who are less hungry and seek social support less frequently.