Objective To study if exercise added to weight loss treatment at the beginning of the weight loss intervention or at 6 months could sustain the weight loss achieved or give extra boost for weight reduction.

Design 36-month, 4-group parallel, randomized trial.

Setting Oulu, Finland.

Participants 120 obese adults (body mass index ≥ 30).

Intervention Participants were randomly assigned to behavioural modification (iBM) (n = 30), behavioural modification + exercise from 0 to 3 months (CWT1) (n = 30), behavioural modification + exercise from 6 to 9 months (CWT2) (n = 30), and a control group (CON) (n = 30). Questionnaires and measurements were performed at baseline, 3,9,4 and 36 months. The intervention consisted of an intensified weight loss period (1-12 months) followed by a weight maintenance period (13-36 months). Intensified behavioural modification included 14 individual face to face meetings, eleven times with a personal therapist (qualified nurse) and three times with a nutritionist. Weight maintenance period included six individual meetings with personal therapist. Twelve weeks supervised exercise was offered three times a week, 40 minutes at a time. In the CWT1 group supervised exercise was offered at months 1-3 and in the CWT2 group at months 4-6.

Measurements Body weight (primary outcome) and waist circumference (secondary outcome)

Inclusion Criteria:

• Body mass Index > 30
• Age 18-64

Exclusion Criteria:

• Pregnancy
• Health reasons preventing exercise and exercise test
• Medication preventing exercise and exercise test
• Previously diagnosed diabetes