Often, as we eat less, our bodies expend calories at a slower rate (that is, our metabolism decreases). Perhaps this occurs to ensure our survival, or just to defend a comfortable body weight. In any event, this slowdown is a real
phenomenon, and has been shown in many laboratory studies — it's called diet induced adaptive thermogenesis. If your calorie expenditure falls, it can be increasingly difficult to take in few enough calories to lose weight. This can
be quite a frustration and challenge to the person trying to shed some pounds.
So, while it's nice to have an equation that works in the lab, the 3500-calorie figure may not play out so tidily in reality. However, it can serve as a goal if you are trying to lose weight. By cutting 500 calories a day (a total of 3500 per week), and otherwise eating a balanced diet, you may find you lose approximately a pound a week. This rate of
weight loss is considered reasonable and healthy.
While simple math might suggest that one could cut thousands of calories per day and shed pounds in the blink of any eye, more realistic and lasting weight change happens gradually. Skipping meals can actually have a negative impact on weight management. To keep your metabolism speeding along, consider having 4 or 5 smaller meals and snacks throughout the day. In addition to providing consistent energy and maintaining your metabolism, you may be more likely to resist those "snack attacks" that happen with extreme hunger. Finally, an important factor in keeping your metabolism moving is participating in regular exercise, which is good for you regardless of whether you're trying to lose weight or just curious about calories.