The outcome of the intervention was in one sense quite significant - at 3 months the women randomly assigned to the interventionist led group reported performing nearly 4x as much exercise as the women randomly assigned to a self-directed intervention. Unfortunately though, by month 12, that difference shrank to the point of no longer being statistically significant.
Why did their exercise drop off so much?
Perhaps it was because of the fact that exercising more at 3 months didn't result in any increase in weight loss for the interventionist led group, which, like it does with gym goers every New Year's season, may have led those folks exercising more at month 3 to have long since given up exercising more by month 12 following the repeated frustration of scales that didn't do what was hoped of them.
Overselling exercise's benefits to weight while underselling its benefits to health, does a disservice to both.