Journal Title (Medline/Pubmed accepted abbreviation): Int. J. Sport Nutr. Exerc. Metab.
Page numbers: 97-104
doi (if applicable):
Summary of Background and Research Design
Background: Athletes sometimes aim to lose weight in order to increase their power-to-weight ratio. When weight is cut too quickly, the athlete can also lose lean body mass (LBM; muscle), potentially impairing their ability to perform at a high level.
Hypothesis: A slow reduction in body weight will be more effective at preserving lean body mass, strength, and power compared to a fast reduction in body weight.
Subjects: Elite male (n=11) and female (n=13) athletes, age 18-35 yr. old. Subjects were recruited when they called in to get advice on weight loss or were invited to join the study.
Experimental design: randomized to one of two interventions: slow reduction (SR) or fast reduction (FR) of body mass
Protocol: Subjects participated in the weight loss/strength training protocol until their desired weight loss was reached (minimum 4% of initial body weight). Depending on the rate of weight loss assigned, this took 4-12 wks. Athletes worked closely with nutritionists to develop a very specific, personalized diet plan to achieve the weight loss goal at the proper rate. Athletes continued their regular training for their sport, and in addition came to the Olympic Sports Center in Norway 4 times per week for strength training. Performance was measured by a 40 m sprint, countermovement jump (CMJ), and determination of their 1-repetition maximum (1RM) of bench press, bench pull, and squat. Before and after intervention, the athletes completed an eating disorder inventory (EDI) evaluation. This evaluation inquired about psychological and behavioral attitudes toward eating and can be used to identify traits associated with eating disorders such as anorexia and bulimia.
Summary of research findings:
- There were 3 athletes in the SR group and 5 athletes in the FR group who did not achieve their weight loss goals but are still included in the analysis. When their data are removed the overall conclusions do not change; differences between the SR and FR groups are more distinct.
- Those in the SR group spent 8.5 ± 2.2 wks in intervention and those in the FR group spent 5.3 ± 0.9 wks.
- Energy intake was reduced 19 ± 2% in the SR group and 30 ± 4% in the FR group.
- Body weight was reduced 5.6 ± 0.8% in the SR group and 5.5 ± 0.7% in the FR group.
- The rate of weight loss was 0.7 ± 0.4% per week in the SR group and 1.0 ± 0.4% per week in the FR group.
- Fat mass decreased 31 ± 3% in the SR group and only 21 ± 0% in the FR group (p = 0.02).
- Lean body mass increased 2.1 ± 0.4% in the SR group and was unchanged in the FR group (increase of -0.2 ± 0.7%, p < 0.01).
- When looking at gender differences, women in both groups gained lean body mass during the intervention while men only in the SR group gained lean body mass.
- Performance in the CMJ was higher in the SR group pre vs. post, while there was no significant change pre vs. post in FR (difference in change between groups was not significant). In the SR group, there was a significant change, pre-vs. post, in 1-RM bench press vs. no change in the FR group (difference in change between groups was significant). Like the CMJ, there was a significant increase in the SR group pre vs. post, but no pre vs. post change in FR (difference in change between groups not significant). Both groups had significant pre vs. post differences in squat, but the changes between groups were not significant. There were no significant within or between group changes in the 40-m sprint.
- There were no significant differences in EDI scores between groups after intervention.
Interpretation of findings/Key practice applications:
A slower weight loss strategy (0.7% of initial body weight per week) is more effective for simultaneously increasing lean body mass. Weight loss rates of 1.0-1.4% are possible while maintaining strength and power. Additional, intense strength training may be required to achieve these results.
The athletes were assessed for strength and power when they achieved their weight loss goal, and therefore the time of the intervention differed by about 3 wks. It would have been interesting to see the strength/power performance of the athletes after the same duration of intervention. For example, could those in the FR group increase their strength and power to equal (or exceed) that of the SR group in the last 3 wks of the trial, after their ideal weight was achieved?
In addition, the athletes in this study were already relatively lean at baseline. It might be interesting to see how these rates of weight loss would have impacted athletes having a higher initial degree of body fat.