Successful Dieting [5/5]: What Is The Best Weight Loss Rate?



The composition of weight loss is important. While greater deficits yield faster weight loss, this strategy makes you lose more lean body mass than slower weight loss programs due to the size of the caloric deficit, and dietary factors. For example, resistance exercise or high protein diets may modify the proportion of weight loss resulting from body fat versus lean tissue (1,2,3).

Lean body mass is lost in concert with body fat during weight loss (4,5). As the size of the caloric deficit increases weight loss coming from lean body mass also tends to increase (6,7,8). 

As I have argued before, not all diets can be considered successful, the importance of keeping lean body mass loses to a minimum during a diet is paramount. That is, the ratio of body fat to lean mass should be high, for example 80% of fat mass to 20% of lean mass.

The higher the initial body fat, the greater the required cumulative energy deficit required to produce a given amount of weight loss. This has implications for women, since women typically have more body fat than men of similar body weight, and this may explain why men tend to lose more weight than women for a given energy deficit (6). However greater weight loss is associated with a lower average cumulative energy deficit meaning that over time more weight is lost for the same degree of energy deficit (6).

Another fact to keep in mind is that weight loss typically slows over time for a prescribed constant diet (6,9) suggesting that either the energy expenditure decreases with time, or the dietary intervention is relaxed over time, or both (6).

The energy deficit is closely related with the loss of body weight rate per week.

A study compared changes in body composition, strength, and power during a weekly body-weight (BW) loss of 0.7% slow reduction (SR) vs. 1.4% fast reduction (FR) (8). Twenty-four athletes followed energy-restricted diets promoting the predetermined weekly WL. They consumed about 1.2–1.8 g/kg of daily protein, 3.2–3.6 g/kg of daily carbohydrate (54-55.5%) and ≥20% of fat.


BW and fat mass decreased in SR (0.7%/week) by 5.6% and 5.5%, and decreased in FR (1.4%/week) by 31% and 21%, respectively. LBM increased in SR by 2.1% whereas it was unchanged in FR.

Results show that a total body weight loss rate of 0.7-1.4% per week doesn’t cause lean body mass loss (8).

Another study by the same authors studied the effect of WL rate on long-term changes in body composition and performance in 23 elite athletes 6 and 12 months after 2 different weight loss interventions promoting loss of 0.7% vs. 1.4% of body weight per week (10).

Body mass decreased by 6% in both groups during the intervention but was not different from baseline values after 12 mo. Fat mass decreased more in SR (31%) than FR (23%) but was not different from baseline after 12 mo. Lean body mass and upper body strength increased more in SR (2.0% and 12%, respectively) than in FR (0.8% and 6% respectively) during the intervention, but after 12 mo there were no significant differences between groups in body composition or performance.

No significant differences between groups were observed after 12 months compared to baseline, suggesting that weight loss rate is not the most important factor in maintaining body composition and performance after weight loss in elite athletes (10).

In another study of weight loss rates in strength training women, weekly losses of 1 kg over 4 weeks resulted in a 5% decrease in bench press strength and a 30% greater reduction in testosterone levels compared to 0.5 kg per week (11).

Weight loss rates of 0.5-1.4% per week are advisable to keep lean body mass loss to a minimum. Rates closer to the low end (0.5%) are safer.

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References

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