Weight loss by mobile phone: a 1-year effectiveness study.

OBJECTIVE To investigate the short- and long-term effectiveness and the predictors of weight loss in a mobile phone weight-loss programme among healthy overweight adults. DESIGN One hundred and twenty-five healthy, overweight (BMI = 26-36 kg/m2), 25-44-year-old, screened volunteers were randomized to an experimental group (n 62) to use a mobile phone-operated weight-loss programme or to a control group (n 63) with no intervention. Via text messaging, the programme instructed a staggered reduction of food intake and daily weight reporting with immediate tailored feedback. Assessments were at 0, 3, 6, 9 and 12 months for the experimental group; at 0 and 12 months for the control group. Main outcome variables were changes in body weight and waist circumference. RESULTS By 12 months the experimental group had lost significantly more weight than the control group (4.5 (sd 5.0) v. 1.1 (sd 5.8) kg; F(1,80) = 8.0, P = 0.006) and had a greater reduction in waist circumference (6.3 (sd 5.3) v. 2.4 (sd 5.4) cm; F(1,80) = 55.2, P = 0.0001). Early weight loss, self-efficacy, contact frequency, attitudes towards the medium, changes in work and family life and changes made in dietary habits were the strongest predictors of weight loss. CONCLUSIONS This mobile phone weight-loss programme was effective in short- and long-term weight loss. As a minimum-advice, maximal-contact programme, it offers ideas for future weight-loss programmes.