Resting Metabolic Rate in Female Fitness Athletes before, during and after Fitness Competition: A prospective cohort study investigating the consequences of dieting on RMR

Abstract

Objectives: Body image idealization and appearance is a never-ending debate in society. The past five to eight years a rapid increase in popularity in competitions focusing on body, muscle development and appearance, such as different fitness categories has been observed. Yet, there is lack of research and knowledge on health effects from such a lifestyle. Hence, the aim of this study was to examine if four months of dieting leading up to a fitness competition leads to any change in RMR in female fitness athletes, and whether or not any potential change in RMR will be reversed when the fitness athletes returns back to their normal diets.

Methods: Data used in this study was collected from a larger research project named “Fitness Health”, a prospective cohort study examining the effect of a fitness lifestyle on competitive female fitness athletes. A physically active, age matched, female population was recruited as a control group. RMR was measured through indirect calorimetry, at three points; 1) before their preparatory diet was initiated (3-4 months pre-contest), 2) two weeks prior to the contest and 3) one-month post competition. A final sample of 46 participants, n=22 Fitness athletes and n=24 physically active controls were included in the study.

Results: A significant decrease (-184 ±46 kcal/day, p=.002) in RMR was detected after four-months of dieting in female fitness athletes. One-month post competition RMR was increased compared to 2 weeks pre contest (326 ±74 kcal/day, p=.001). There was no significant difference in mean RMR one-month post competition compared to baseline (p=.294). No significant effect over time in mean RMR was found in PA controls (p=.174).

Conclusion: A significant change in RMR was observed in fitness athletes after four months of dieting leading up to a fitness competition. However, one-month after competition RMR values were reversed back to baseline levels.