To evaluate the effect of a tailored behavior change program on a composite lifestyle change score. A randomized controlled trial conducted in Belgium in 2007-08 with 314 participants allocated to a control and an intervention condition. The intervention was a tailored behavior change program (web-based and individual coaching). The dose of the coaching was chosen by the participants and registered. Outcome measures were weight, saturated fat intake, fruit and vegetable intake, physical activity, smoking status and a composite lifestyle change score. Mann-Whitney U-tests, Kruskal-Wallis tests, t-tests and one-way analyses of variance were used to compare the study conditions and three intervention dose groups (no/low, medium and high intervention dose). There were no significant differences between the study conditions or between the intervention dose groups for the individual lifestyle factors. The composite lifestyle change score was significantly higher in the high intervention dose group compared with the no/low intervention dose group (P = 0.009). The composite lifestyle change score was positively related to the intervention dose, while the individual lifestyle factors were not. Behavior change programs that target multiple lifestyle factors could be evaluated by using a composite lifestyle change score taking into account the intervention dose.