Is rapid weight loss bad for body composition?

Energy balance is the most important factor to lose weight; energy expenditure must exceed energy intake.

While aggressively dieting may increase fat loss, it may also increase muscle mass loss. Therefore, it can be questioned if losing weight as fast as possible is the best strategy.

The current study investigated the effect of two different rates of weight loss on body composition. One group lost weight pretty fast (1% of bodyweight per week), the other group lost is more slowly (0.7% bodyweight per week).

It took the aggressive dieting group ~5.3 weeks to lose 4.2 kg bodyweight. It took the slower dieting group ~8.5 weeks to lose this amount.

While both groups lost the same amount of weight, the composition of the lost weight was different. The aggressively dieting group lost more muscle and less fat compared to the slower dieting group.



Therefore, this study suggests that more aggressive weight loss goes at the expensive of muscle mass gains.

In conclusion, aggressive dieting is effective for rapid weight loss, but suboptimal for muscle mass.

Study:

Garthe et al, Effect of two different weight-loss rates on body composition and strength and power-related performance in elite athletes, Int J Sport Nutr Exerc Metab, 2011

Go to the next infographic in the dieting series:

Diet breaks increase fat loss?