|Messing with your hormones won't help to reveal your abs, ladies!|
So if you are wondering, why your menstrual cycle is messed up. Why you cannot get pregnant or why you simply stopped menstruating, ladies, this article is for you.
Needless to say that the same goes for male and female trainers, obviously, for whom the results of a very recent study from the Pennsylvania State University and the Penn State University College of Medicine (Williams. 2014).
The study Nancy I. Williams and her colleagues conducted was designed to confirm or refute the that there would be a dose-response relationship between the induction of menstrual disturbances (luteal phase defects, anovulation, and oligomenorrhea) and the magnitude of energy deficiency.
In other words, the researchers expected that higher energy deficits would incur a significantly greater incidence and more severe disturbances of their menstrual cycle disturbances. To evaluate their hypothesis, the researchers conducted a randomized prospective design that employed controlled feeding and supervised laboratory-based exercise over the course of three menstrual cycles in young, untrained, premenopausal, eumenorrheic women.
The study was conducted with healthy young, weights-stable women, who had not evidence or history of disordered eating were aged 18 – 30 years, weighed 45 – 75kg and had a normal body fat level of 15 – 35%. The women didn't smoke, were not hormones or anti-contraceptives.
"The study was conducted over three years, with yearly cohorts recruited in the fall of the academic year and followed until the end of spring semester. The controlled feeding and exercise training began after the Screening and Baseline periods, each period lasting one menstrual cycle. All phases of the intervention were anchored to subjects’ menstrual cycles, and each study phase consisted of one menstrual cycle (Intervention Cycle 1, Intervention Cycle 2, Intervention Cycle 3). A post study period of one week where diet and exercise remained controlled allowed for post intervention measurements. The study design is illustrated in Table 1.
Table 1: Overview of the experimental procedures; MC=Menstrual Calendar | Note: Mid-study Body composition testing occurred during Intervention Cycle 2 for most subjects, but in some it occurred during Intervention Cycle 3 (Williams. 2014)
Group assignments were based on varying levels of energy deficiency created through a combination of caloric restriction and exercise such that one group remained in energy balance and four groups were in different degrees of an energy deficit. Repeated assessments of menstrual status, metabolic status, and body composition were conducted." (Williams. 2014)
So what did the scientists do?
During the Baseline period, subjects were randomly assigned to an experimental group for the Intervention Cycles 1, 2, and 3 of the study. The goal of the subject groupings was to test the impact of varying levels of an energy deficit created by the combination of caloric restriction and exercise on menstrual function.
|Table 2: Baseline demographic characteristics of study subjects categorized by group (top) and energy balance parameters averaged across Intervention Cycles 1-3 for each group (bottom) - directly from Williams (2014)|
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|Figure 1: Daily energy deficit (left) and corresponding menstrual irregularities (right) the Pennsylvanian researchers observed during the intervention (Williams. 2014)|
Next to the menstrual irregularities, which were obviously what the scientists were actually interested in, the scientists also observed that the 34 subjects lost weight, 3.8 kg in the ED1 and - listen up ladies! - only 2.8 kg and 2.6 kg in the high(er) energy deficit groups ED2 and ED3 (no significant weight loss occurred in the exercise only, i.e. the EXCON group).
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- Williams, Nancy I., et al. "Magnitude of daily energy deficit predicts frequency but not severity of menstrual disturbances associated with exercise and caloric restriction." American Journal of Physiology-Endocrinology and Metabolism (2014): ajpendo-00386.