Well I interpreted his work differently as they seem to focus on the weight loss.
They were trying replicate the weight loss that happens with baratric surgery. They also don't seem to know why it works for some and not others. I believe the next step is to look at those that are not classed as overweight.
As I understand it, the weight loss is there primarily to increase capacity. That's why they use a percentage weight loss rather than a specific value. But it's pretty clear that it does need to happen.