I wanted to further discuss a study I mentioned in the last post. In this study, subjects exercised 60 minutes a day, 6 days a week for a year, but only lost 4 pounds. However, in a study I've mentioned before, subjects exercised for roughly 60 minutes a day, 7 days a week for 3 months. Subjects lost 16 pounds over the 3 months.
So why did subjects lose weight in one study and not the other? You can probably guess the answer: diet. In the 12 month study, subjects were free to eat what they wanted. In the 3 month study, subjects were told to consume the amount of calories per day that they were consuming prior to the study. In other words, their calorie intake was kept constant while their calorie expenditure was increased. This led to the weight loss.
These results show a couple things. First, if exercise is increased with no regard to diet, it is likely that the body will compensate with increased hunger/eating and therefore the result will be minimal weight loss. Second, the good news is that the subjects who exercised an hour a day did not gain weight, regardless of what they were eating.
Fasted exercise may be effective because it's an easy way to create a calorie deficit on the day a person exercises. If you fast, workout, fast some more, and then eat, it's likely that the net result for a day will be a calorie deficit. A person might be able to achieve the same result by consuming the same amount of calories over the course of the day but without the fast. This would make a good research study!