If we assume that dropouts had the same distribution of change as the subjects in the control group, then what is the probability that an active subject who complied with the  intervention lost at least 1 kg/m²? 

It was known that only 70% of the subjects in the active group actually complied with the intervention; that is, 30% of subjects either dropped out or did not attend the required group and individual counseling meetings. We will refer to this latter 30% of subjects as dropouts.