However, contrary to your headline, it tells us nothing about the benefits of losing weight. Some 150 people who had active intervention lost more than the same number in the control group. So what?
The study apparently says nothing about how many of either group went on to develop bowel cancer, so I cannot understand how it could be concluded from it that “it is estimated that almost half of bowel cancers could be prevented by maintaining a healthy weight and diet”.
Proper research would have to use a much, much larger sample, tens of thousands rather than a few hundred, and follow the subjects for long enough – far longer than one year – to assess disease incidence.
If your report is accurate, this study tells us nothing we didn’t already know; it’s merely yet another example of the Hawthorne Effect