A new (March 2018) study looked into some of the physiological changes that occur in natural bodybuilders.

While most of these changes are obvious it can be good to have some clearer numbers on how much of an impact preparing for a contest can have.

The 9 bodybuilders were assessed at 4 points:

  1. 16 weeks pre-contest

  2. 8 weeks pre-contest

  3. 1 week pre-contest

  4. 4 weeks post contest


  • Body composition

  • Resting metabolic rate (RMR)

  • Hormones

  • Food & training diaries

During the 16 weeks pre-contest until contest week

  • Calories reduced by 220 from 3000 to 2780

  • Protein averaged around 250g a day

  • Body Fat went from an average of 10.5% to 6.5%

  • Testosterone dropped by ~38%

  • Free Testosterone dropped by ~50%

  • IGF-1 dropped by ~25%

  • Maintained almost all lean mass (-0.7%)

  • RMR was unaffected

“The reduction in anabolic hormone concentration is likely attributable to the prolonged negative energy balance, despite a high dietary protein intake.”

The high protein intake is likely the reason why they only lost a very small amount of lean mass. High protein diets are known for their protein sparing effect.

One of the key questions is how well did they recover afterwards?

The good news is most participants were back in the 10% range of body fat within 4 weeks and hormone levels were almost back to pre contest prep levels. From other research seen in this area, it does seem like as long as the body is giving a good period of time to recover (higher calories and body fat %) there is generally no long term damage. This is why you should structure a post contest plan and not compete too frequently.

In many ways it shows that for the majority of male natural trainees, trying to maintain 5-8% body fat is not ideal from a health perspective. 10-12% is more realistic and maintainable.

What effects have you seen from your own contest preps?