A recent 2017 study looked into the potential consequences of dieting for a fitness competition and whether these could be reversed using a “recovery period”

27 Female competitors finished the study. 17 Bikini Fit, 9 Body Fitness and 1 Fitness. Diet periods lasted ~20 weeks.

The dieting strategy used was common of contest preps, in that carbs were reduced and more cardio added over time.

Now it’s important to note that a reduction in upto 50% of your body fat is a lot and going to have a large impact on your hormonal balance.


During the diet

  • Calories were reduced by ~23% from start to finish. Mainly through reduced carbs

  • Average body fat went from 23% to 13%

  • 35-50% decrease in body fat

  • ~12% decrease in total body weight

  • Cortisol levels remained stable

  • Testosterone reduced by ~40-50%

  • Estradiol and Leptin reduced by over 50%

  • T3 reduced by ~30%

  • Main mood complaint was a “lack of vigor”

  • 3 of the 27 had missed menstrual cycles

  • 10 of the 27 had irregular menstrual bleeding


Again the key thing to look at is whether any of these changes were permanent and how successful a recovery period would be.


Recovery Period Conclusions

Fortunately the 3-4 month recovery period was successful in returning most parameters to baseline. The two exceptions to this were free T3 and testosterone which did not recover as quick. Looking at other research it is likely these will eventually return to baseline, but may take longer.

“This study shows for the first time that most of the hormonal changes after a 35–50% decrease in body fat in previously normal-weight females can recover within 3–4 months of increased energy intake.”

Again I’ll repeat my previous advice, from a health perspective getting to a super low body fat % will inevitably have a negative impact on your physiology. So it is crucial that you give your body time to recover after. A basic estimate is to give yourself at least the same length recovery period as that you dieted. So if you diet for 3 months, you should give yourself 3 months afterwards in a recovery period of higher calories. Strategies such as reverse dieting can also be used to help minimise excess fat regain.

Resources:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5222856/