We have a natural tendency to store fat, our survival mechanism in times of famine. But these are days of abundance for many, who binge on energy-dense fatty and sugary foods without engaging in energy-burning physical activity. The result: obesity. To expend energy and increase our use of stored fat and carbohydrate, do exercises that use the large muscles of arms and legs—e.g., walking, jogging, swimming, cycling, aerobics—and do them in prolonged durations.
2 main factors determine how many calories you burn:
- Duration. Walking 3 kilometers uses almost the same amount of energy as running 3 kilometers. But walking the 3 kilometers will take longer than running the same distance.
- Intensity. Jogging for 30 minutes will use more energy than walking for 30 minutes, since you cover a greater distance jogging than walking. Intensity also influences the amount of fat and carbohydrate that you use. Low-intensity exercise, such as walking, uses fat and some carbohydrate. The harder you exercise, the greater the proportion derived from carbohydrate.
Vigorous exercise uses carbohydrate (muscle glycogen), but it also reduces your fat stores. When your glycogen is depleted, some of the carbohydrates you eat will replenish the glycogen you used up, so you are less likely to store excess carbohydrate as fat. The ideal is to find a balance between vigorous exercise and reasonable duration (30 to 60 minutes per day). It may be better to walk for an hour than to jog for five minutes, but it is more effective to walk briskly (or jog) than to walk slowly.