A Science-based Review of Physiological Changes During A Natural Bodybuilding Contest Prep

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Contest Prep Changes
Natural bodybuilding is becoming an increasingly popular sport.  When I started competing 10yrs ago, large natural pro qualifiers had around 50 competitors.  These days basically every natural pro-qualifier has 100+ competitors, some as high as 200-300+.  However, despite the popularity of the sport, very little research has been done on physiological changes that occur in natural bodybuilders using a more modern science-based approach to the sport.  We all know from experience that during contest prep we generally eat less food, do more cardio, and feel tired, hungry and downright miserable at times.  In addition, it is not uncommon to lose some performance in the gym and some muscle mass along the way.  However, what is really going on during contest prep?  The purpose of this article will be to summarize research on physiological changes during bodybuilding contest prep, with focus on 2 recent case studies following natural pro bodybuilders during contest prep.

Bodybuilding Research:

If you type the words “bodybuilding” or “bodybuilder” in to pubmed or your favorite scientific article database, the vast majority of studies you will find focus on negative health consequences associated with use of steroids, growth hormone, and other anaoblics in bodybuilders such as: acne [1, 2], cardiovascular disease [3-6], kidney problems [7, 8], liver problems [9], respiratory problems [10], early onset diabetes [11], muti-organ dysfunction [12], and rhabdomyolysis [13].  Others focus on negative effects of oil injections [14-16], diuretics [17, 18] and even psychological disorders [19, 20] in bodybuilders.

The referenced studies above are only a selection of the studies out there.  However, in the vast majority of these studies, the authors attribute these negative health effects of the sport to drug use by bodybuilders.  Whether drug use was or wasn’t the cause of the adverse effects of bodybuilding listed above is beyond the scope of this article;

however, what I want you to take home from this is that despite all of these studies, there is very little information out there on the physiological changes that occur during bodybuilding contest prep.

Previous studies on bodybuilders contest prep:

Several studies, primarily from about 20-30 years ago, have characterized contest prep using what most of us today would consider “bro” methods. In addition, many of these studies [21-28] looked at competitors who were using performance enhancing drugs. Here are some examples of approaches reported in these studies:


  • Average calorie intake as low as <900 cals/day in women [29]
  • Incredibly low fat intake including as low as 9g/day in women [29] and 19g/day in men [22]
  • High protein – in fact, one study reported protein intake as high as 85% of calories [26]
  • Complete elimination of certain foods and food groups including: dairy, egg yolks, red meat, and sugar [21, 27, 29]
  • Eating as often as 10x per day [21]
  • Restricting carbs before bed [21]
  • Binging during prep reported [21] 


  • 3 to 10+ hrs/wk steady-state cardio [24, 25, 29]


  • Rep range increased during contest prep [21, 22, 25] which likely contributed to strength decreased observed during the course of contest prep [22]

Peak Week:

  • Sodium and water restricted [21, 28]

Length of Contest Prep and Rate of Loss:

  • Very short contest prep durations. One study reported that only 55% of males and 75% of females prepped for at least 2 months [28]
  • As a result, rate of weight loss of as high as 4lbs/wk was reported [27]

Contest Prep Changes
Despite these approaches, most of these competitors lost roughly 2-4lbs of fat mass for every 1 lb of lean mass lost [21-24, 27, 30, 31]. This allowed them to get down to contest shape and in the studies that reported contest results, many of the bodybuilders studied placed very high in their classes [21-24, 27, 28, 31, 32]. However, there were also negative health effects of the contest prep process including amenorrhea [28, 33, 34], and many vitamin and mineral deficiencies [25, 27-29, 31, 32], the most common of which was calcium due to the fact that most bodybuilders during this time period typically eliminated dairy from their diet during contest prep.

In addition, the bodybuilders studied reported becoming more fatigued, depressed, tensed, and confused during contest prep [23].

One side note that I found particularly interesting is the rate at which competitors gained weight post-contest when they went back to their offseason diet rather than reverse dieting back to their pre-contest weight. For example, a 25yr old male was followed for 4 months pre-contest. During this time he lost around 23lbs; however, 3 weeks post-contest he gained around 30lbs which left him 7lbs heavier than the start of contest prep [21]. Similarly, 6 females were who were followed for 4 weeks post-competition gained an average of 19lbs [29] and another group of 6 females gained an average of 8.5lbs in the 4 weeks following the contest [32]. In a much shorter time-frame, a 27yr old male bodybuilder gained 17lbs in 2 days post-contest [27].

Recent Natural Bodybuilding Case Studies

Although the approaches used in these studies and the results may be of interest to those of us in the natural bodybuilding world, they do not reflect the physiological changes that occur during natural bodybuilding contest prep using more modern methods. The following section will review 2 recent case studies examining physiological changes during natural bodybuilding contest prep [35, 36].

Table 1. Background Information

  Bodybuilder A [35] Bodybuilder B [36]
Age (yrs) 26-27 26
Gender Male Male
Rank Natural pro bodybuilder Amateur, awarded pro status at end of prep
Length of Prep 6 months 6 months


Table 2. Contest Prep Diet

  Bodybuilder A [35] Bodybuilder B [36]
Start of Prep 36% pro, 36% carb, 28% fat 5 days/wk, 30% pro, 48% carb, 22% fat 2 days/wk 250g pro, 240gC, 70gF 5 days/wk, 225g pro, 400gC, 65gF 2 days/wk
During Prep 5-10g reductions in carbs/fat made based on progression 5-10g reductions in carbs/fat made based on progression
End of Prep 46% pro, 29% carb, 25% fat on average 250gP, 140gC, 51gF 5 days/wk, 225gP, 255gC, 46gF 2 days/wk


Table 3. Training and Cardio

  Bodybuilder A [35] Bodybuilder B [36]
Training 4 days resistance training/wk            5hrs average, frequency 2x/wk 5 days resistance training/wk,         5-7.5hrs/wk, frequency 2x/wk
Cardio Average: 1 day HIIT 40min/wk1 day
steady state 30min/wk
Beginning: 2x40min HIIT
End: 4x60min HIIT
2x30min steady-state


Table 4. Body Composition Changes During Contest Prep

  Bodybuilder A [35] Bodybuilder B [36]
Body Weight 226.3 lbs to 195.5 lbs (-30.8 lbs) 200.4 lbs to 163.5 lbs (-36.9 lbs)
Lean Mass 192.8 lbs to 186.6 lbs (-6.2 lbs) 165.4 lbs to 151.4 lbs (-14.0 lbs)
Fat Mass 33.5lbs to 8.9lbs (-24.6 lbs) 35.0 lbs to 12.1 lbs (-22.9 lbs)


Table 5. Performance Changes During Contest Prep

  Bodybuilder A [35] Bodybuilder B [36]
Big 3 1 RM Decreased Not Measured
Cycling Power Decreased Not Measured
Relative Vo2 Max No Change Increased


Table 6. Changes in Mood and Markers of Bone and Cardiovascular Health during Contest Prep

  Bodybuilder A [35] Bodybuilder B [36]
Mood Worsened Not Measured
Bone Mineral Content No Change Increased
Blood Pressure Decreased Decreased
Heart Rate Decreased Decreased
Arterial Stiffness Decreased Decreased
Autonomic Function Not Measured Decreased


Table 7. Changes in Blood Markers during Contest Prep

  Bodybuilder A [35] Bodybuilder B [36]
Testosterone Decreased Not Measured
Insulin Decreased Not Measured
Cortisol Increased Not Measured
Thyroid Hormone Decreased Not Measured
Grehlin Increased Not Measured
Leptin Decreased Not Measured
Total Cholesterol No Change No Change
HDL Increased Not Measured
LDL No Change Not Measured
Inflammation Not Measured No Change
Oxidative Stress Not Measured No Change

Contest Prep Changes

Take Home Points:

  • Although numerous previous studies of bodybuilders, primarily using performance enhancing drugs and “bro” prep methods, observed negative effects of bodybuilding contest prep, 2 recent case studies using a more modern science-based approach to contest prep observed minimal adverse effects.
  • Natural bodybuilding contest prep results in fat loss, lean mass loss, decreases in performance, and hormonal changes, even in elite natural bodybuilders.
  • Natural bodybuilding contest prep may improve bone density and cardiovascular health.
  • One potential negative effect of contest prep even with more modern methods is a potential worsening in mood in the later stages of prep. However, this is far less severe than the adverse effects previously reported in studies on bodybuilding contest prep.


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