The following question is often asked: Is it better to lose weight slowly or quickly? Most experts say it is best to lose weight slowly because slower weight loss is more sustainable and may be healthier because it carries less risk of nutrient deficiencies and usually results in less muscle loss. On the other hand, data from the National Weight Control Registry suggests that dieters who lose weight rapidly are just as likely as slow weight losers to sustain their weight loses over the long term.

But how about athletes? It seems reasonable to speculate that rapid weight loss is less advisable for athletes than for non-athletes because of its potential for detrimental effects on performance. And a new study from the Norwegian School Of Sport Science suggests that slow weight loss is indeed the better way to go, at least for strength and power performance. 

Thirty “elite” athletes participated in the study. They were divided into two groups. Members of one group adjusted their diet to accomodate a target weight loss rate of 0.7 percent per week. Members of the other group aimed to lose weight at twice that rate. All of the subjects continued on their respective diets until they reached their goal weight or for 12 weeks - whichever came first. In addition, all of the subjects lifted weights four times per week (in addition to doing their normal training) to minimize muscle mass losses.

Members of both groups lost equal amounts of weight, which I think suggests that most of the subjects were able to reach their goal weight. The abstract does not say whether the fast weight loss group got actually there faster - that would be very interesting to know. But overall, members of the slow group got better results. While body weight changes were similar, members of the slow weight loss group lost significantly more fat and gained nearly twice as much muscle.

The athletes were subjected to vertical jump, maximum squat and maximum bench press tests before and again after dieting. Members of both groups improved their performance in all three tests, but the slow weight losers improved more (8.0 percent to 4.3 percent in the vertical jump, 13.1 percent to 9.7 percent in the squat and 15.1 percent to 7.8 percent in the bench press).

One must be careful not to draw too general a conclusion from this study (for example, it’s possible that rapid weight loss works better for severely overweight non-elite athletes), but it does suggest that slow weight loss is better than fast weight loss for high-level athletes engaged in normal training.