Let’s take a look at how these physiological and psychological responses to low calories affect the real world results of a typical dieter.
Suppose our “typical” dieter is a male who weights 200 pounds and has 18% body fat. His goal is to lose 20-25 lbs.
Before the diet
- 18% body fat
- 36 lbs. fat
- 164 lbs. lean body mass
Like most people, our dieter assumes that the best way to lose the body fat is to starve, so he goes on a 1500 calorie per day diet.
In the 1st week he loses 5 lbs. and is very happy with himself. The second week he loses 4 lbs. Weeks three through six he loses three pounds per week for a grand total of twenty-one pounds lost.
Our dieter now weighs 179 lbs. and he continued to lose weight steadily without hitting a plateau (although the weight loss did slow down). Judging by the scale alone, he has succeeded in his goal, right?
On closer examination, however, we find that he has not been so successful after all.
After the diet
- 179 lbs.
- 14.8% body fat
- 26.5 lbs. fat
- Lean body mass 152.5 lbs.
- Weight loss: 21 lbs.
- Fat lost 9.5 lbs.
- Lean body mass lost: 11.5
By judging his success in terms of body composition instead of scale weight, it becomes clear that he has failed. Fifty five percent of his weight loss came from lean body mass. The drop in lean body mass has decreased his basal metabolic rate so he is now burning fewer calories each day than when he started. This has set him up for a relapse.
Now that the (temporary) diet is “over, “ he goes off his diet.
Few people have the desire or willpower to stay on low calories for long. On a strict calorie and or food restricted diet, almost everyone “falls of the wagon” sooner or later. After a long period of low calories, his body “tricks him” into binge eating by triggering severe cravings and hunger.
Even if he doesn’t binge and he simply goes back to “normal” eating again, his body isn’t burning calories as efficiently as before. Therefore, the number of calories that used to maintain his weight now causes him to gain weight. As the weeks pass, the weight gradually creeps back on until he finally gains back all the fat he lost (plus a little extra for interest).
6 weeks after the diet ends:
- 200 lbs.
- 20.5% body fat
- 41.1 lbs. fat
- Lean body mass 158.9 lbs.
Now he is right back at 200 pounds where he started, with only one difference: He has less muscle, more fat, and a slower metabolism than when he began. He has damaged his metabolism and it will now be harder than ever to lose weight.