To explore which baseline physiological and psychosocial variables predict change in body mass index (BMI) z-score in obese youth after 12 weeks of a dietary weight management study.

Participants were obese young people participating in a dietary intervention trial in Brisbane Australia. The outcome variable was change in BMI z-score. Potential predictors considered included demographic, physiological and psychosocial parameters of the young person, and demographic characteristics of their parents. A multivariable regression model was constructed to examine the effect of potential predictive variables.

Participants (n=88) were predominantly female (69.3%), and had a mean(standard deviation) age of 13.1(1.9) years and BMI z-score of 2.2(0.4) on presentation. Lower BMI z-score (p<0.001) and insulin resistance (p=0.04) at baseline, referral from a paediatrician (p=0.02) and being more socially advantaged (p=0.046) were significantly associated with weight loss. Macronutrient distribution of diet and physical activity level did not contribute.

Early intervention in obesity treatment in young people improves likelihood of success. Other factors such as degree of insulin resistance, social advantage and referral source also appear to play a role. Assessing presenting characteristics and factors associated with treatment outcome may allow practicing clinicians to individualise a weight management program or determine the ‘best-fit’ treatment for an obese adolescent.