Physical exercise is a significant adding to dieting in safe weight loss. Aerobic exercise is an important part of maintaining normal good health as well, especially the muscular strength of the heart. To be helpful, aerobic exercise requires maintaining a target heart rate of above 50 percent of one's maximum heart rate for 30 minutes, at least 3 times a week. Quick walking can achieve this.
 The ability of a few hours a week of exercise to contribute to weight loss can be overrated. To demonstrate, imagine a 100-kilogram man who wants to lose 10 kilograms and think that he eats just enough to maintain his weight (at rest), so that weight loss can only come from exercise. Those 10 kilograms transformed to work are equivalent to about 350 mega joules. (We use an approximation of the standard 37 kilojoules or 9 calories per gram of fat.) Now suppose that his chosen exercise is stair climbing and that he is 20 percent capable at converting chemical energy into mechanical work (this is within measured ranges). To lose the weight, he must rise 70 kilometers. A man of normal fitness (like him) will be tired after 500 meters of climbing (about 150 flights of stairs), so he needs to exercise every day for 140 days (to reach his target).
The minimum safe dietary energy ingestion, without medical regulation, is 75 percent of that needed to uphold basal metabolism. For our imaginary 100-kilogram man, that minimum is about 1,300 calories per day. In condition of combining every day aerobic exercise with a weight-loss diet, he would be capable of losing 10 kilograms in 70 days that is half the time. Certainly, the described system is more careful and would be attractive or suitable for many persons. Consequently, under an efficient but more controllable weight-loss program, losing 10 kilograms (about 20 pounds) may take as long as 6 months.
There are also some straightforward ways for people to exercise, for example: walking sooner than driving, climbing stairs instead of taking elevators, doing more housework with fewer power tools, or parking cars farther and walking to school or the office.
| 
