Consider this an exercise on the laws of unintended consequences.
Vigorous physical activity for at least 45 minutes will strengthen a person’s cardiovascular system and burn calories. It will also make that person hungry. When combined with the general tendency to overestimate calories burned during exercise and to underestimate calories in food defeat is all but guaranteed.
For example, burning 300 calories during an hour’s worth of exercising and eating a delicious 600 calorie muffin as a post workout reward is a net gain. On an average day in which a person exercises more, they eat more.
Weight training builds muscle, and a pound of muscle consumes more calories than a pound of fat but not enough to make much of a difference.
According to calculations published in the journal Obesity Research by a Columbia University team in 2001, a pound of muscle burns approximately six calories a day in a resting body, compared with the two calories that a pound of fat burns. Which means that after you work out hard enough to convert, say, 10 lb. of fat to muscle — a major achievement — you would be able to eat only an extra 40 calories per day, about the amount in a teaspoon of butter, before beginning to gain weight.
The human body is an exquisitely regulated machine which has certain homeostatic goals in mind and works ruthlessly to achieve them. To truly win this war an individual needs to fight against themselves and it is very difficult to do so.
Arm yourself with data about how many calories are really being burned for various types of workout routines and durations. Know the approximate caloric count of your favorite snack foods, like those sugar free muffins at the local bakery.
Plan ahead and be aware of your body’s inclinations. If you are going to be hungry after an energetic workout be sure and have a low calorie and healthy snack immediately available. For a post exercise meal, choose your dining partners carefully.