Except....practically everyone here talking about how they lost weight is also talking about their exercise regimen. Well, the simple physics also shows that exercise has nothing to do with weight loss.
That's far too simplistic. If you do more exercise you burn more calories. That's a fact.
Exercise has to do with redistributing body weight from fat to muscle, which is difficult enough. The only way that exercise commonly affects weight is by water loss from sweat. And the overwhelming majority of the posts in this thread are actually concerned with converting body fat, not reducing body weight. Muscular development requires a great deal of discipline. But it's a different kind of discipline from going hungry, which is how body weight is lost.
The problem is that only extremely
large amounts of exercise or many hours of heavy physical labor to burn enough calories to make a difference. The numbers just don't add up, and the simplistic thinking is to imagine the numbers don't matter. The only practical way for the vast majority of people to make exercise burn enough calories to make a difference is to first restrict caloric intake.
The post above correctly states this in a different form. It also correctly states that the restriction should be rather small. The reason is that large caloric restrictions for more than a day or two does cause undesired effects, such as loss of muscle instead of fat. The post however doesn't state that the healthful weight loss regimen is 1.) rather slow, making the discipline much harder to maintain for no visible results, and 2.) can be accompanied by changes in the BMR. Which brings us back in one sense to the possible role of intestinal bacteria. There's also a role played by roughage but I don't know much about that.