It takes roughly one minute of aerobic exercise to lose 1 gram of fat. However, there are many variables affecting this measure, such as the individual's weight and level of exertion.
The body must run a calorie deficit in order to lose weight. To lose 1 ounce of fat, the body needs to burn 218 calories. With 28.35 grams of fat to an ounce, that rounds to just under 8 calories per gram. It takes about 30 minutes of aerobic exercise to burn 250 calories, or around 8 calories a minute.
It the body is working hard, it burns calories more quickly. If the person is heavier or has more muscle, this also means a faster burn rate.