Physique Athletes Not Prone to Metab./Hormonal 'Damage', Recent Pilot Study in 15 Male & Female Athletes Suggests

Even though the study has male and female study participants this study is still more geared towards the men - why else do we have testosterone, but not estrogen measurements?

As the scientists point out as early as in the title, a recent paper by Trexel et al. (2017) is indeed (at best) a "pilot study" to "evaluate changes in body composition, metabolic rate, and hormones during post-competition recovery" in "physique athletes". In view of the lack of reliable data from the contest preparations o bodybuilders and other physique-sport athletes, even this "pilot" data is more than worth reporting.

That's particularly true, because it is still not clear, as Trexel et al. write whether the "physiological effects of contest preparation persist after competition" and thus whether "they may predispose [...] to preferential gain of fat mass and prolonged, deleterious endocrine side effects" (Trexel 2017)
To answer these questions, Trexel et al. evaluated physiological changes following a physique-based
competition. In that, the scientists actually showed up at the competition and used portable equipment acquire on-site in multiple locations - outcomes included

• body composition, assessed by amplitude-mode ultrasonography and skinfold measurements, 
• body water measured by the means of bioelectric impedance spectroscopy (used only in 8 subjects, because the equipment was not always available), 
• metabolic rate, assessed with a portable indirect calorimetry device (Fitmate Pro, COSMED, Rome, Italy) for 15 minutes, each, and 
• testosterone, c
• cortisol, i
• insulin, g
• ghrelin and 
• leptin assayed via salivary hormone tests, 
because "the on-site nature of data collection precluded the acquisition of blood samples" (Trexel 2017), as well as
• dietary intake, evaluated based 3-day food logs the subjects had to complete one week before the competition (T1) and in the week after the competition (T2)

Altogether the scientists were able to compile data from fifteen physique athletes - 7 male, 8 female drugfree (according to interviews) athletes competing in bikini (n=7), figure (n=1), physique (n=5), or bodybuilding (n=2) classes.

Figure 1: Experimental design. RMR: Resting metabolic rate; BIS: Bioelectrical impedance spectroscopy (Trexel 2017).

The graphical overview in Figure 1 gives you a good idea of when the different parameters were assessed. In that, it is important to note that this study did not as previously discussed studies track the hormonal and metabolic changes over the course of the contest prep - that should be obvious given the specific research focus on possible long-term negative effects of dieting, but in view of the way people often criticize studies for "shortcomings" that are actually a necessary consequence of the research question, I thought I'd better address that right away (see box below for corresponding data).
But let's get back to what the study did measure, namely significant (p<0.05) changes for body weight, lean mass, fat mass and total body water.

Figure 2: Changes in body composition; bars represent absolute values in kg, arrows and. rel. changes; the lean mass increase from T1 to T2, as well as fat gains from T1 & T2 to T3 were stat. sign. (Trexel 2017).

Unsurprisingly, the total body water (TBW | not shown in Figure 2) increased by 5% when the subjects refeeded within days of competition (post-competition data is missing). Hormone-wise, the authors observed that cortisol was higher (p<0.05) at T2 (0.41±0.31 μg/dL) than T1 (0.34±0.31) and T3 (0.35±0.27) - a possible sign of "adrenal fatigue", or rather the downregulation of the central nervous system during prolonged dieting. At the same time, the male testosterone levels recovered at T3 (186.6±41.3 pg/mL) and were significantly greater than at T2 (148.0±44.6, p=0.04), while neither insulin, ghrelin or leptin showed significant changes over time. Further statistical analyses of the data revealed that...

• the changes in testosterone levels in the men were inversely associated (p≤0.05) with the changes in body fat, fat mass and total (r=-0.81--0.88), but not lean mass weight, 
• the individual changes in resting metabolic rate (RMR) were significantly associated (p≤0.05) with changes in body fat percent (ΔBF%; r=0.59) and the protein intake after the contest (T3 | r=0.60); 

The good news for every dieter and physique athlete is that the pre-competition RMR suppression was not markedly variable, as the data in Figure 3 goes to show you, but also "markedly reversed by overfeeding" (Trexler 2017).

Figure 3: Individual responses for resting metabolic rate (RMR) as (A) raw or (B) percent of predicted values. a Significantly greater than T1 (p < 0.05). 2B: Dashed line represents 100% of predicted value (Trexel 2017).

In other words, without reverse dieting, taking thyroid meds and all the other strategies you will read about on the Internet, all subjects bounced back toward normal levels following competition - albeit obviously not without significant fat mass gains over the 4-6 weeks immediately after the competition.
References:

• Cunningham, John J. "Body composition as a determinant of energy expenditure: a synthetic review and a proposed general prediction equation." The American journal of clinical nutrition 54.6 (1991): 963-969.
• Trexel et al. "Physiological Changes Following Competition in Male and Female Physique Athletes: A Pilot Study" International Journal of Sport Nutrition and Exercise Metabolism (2017) [Published manuscript].