Last year, a study showed that supplementing with prebiotics could produce weight loss. The weight loss was relatively small: 2.2 pounds over 12 weeks.
Another study has been done to determine the mechanism behind this weight loss. In the first study, subjects took 21 grams of prebiotics per day, and in the second study they took a slightly lower amount, 16 grams per day. The second study, however, went into more detail about subjects' food intake.
The subjects consuming prebiotics averaged 2,339 calories per day while the subjects consuming the placebo consumed 2,501 calories per day.
This is pretty significant in my view. Without altering any other diet parameters other than adding prebiotics, subjects consumed 162 less calories per day. This could lead to gradual weight loss like I talked about in this post.
Looking at it the other way, the lack of prebiotics and/or the lack of healthy gut flora could lead a person to consume 162 more calories per day than they usually would.
When researchers talk about how our mechanisms matching calorie intake and output are off by a little bit, bacteria seems like the prime candidate. Earlier generations with healthy gut flora kept their calories and weight in balance. Today, the average person's gut bacteria is disturbed, leading to high rates of obesity and chronic disease.