Hormones and dieting

I was reading a paper last night from the International Journal of Sports Physiology and Performance (yes, I am a nerd) that was essentially a case study of a male bodybuilder for the 6 months leading up until competition and for the 6 months following it.

During that period they measured a number of things including body fat, lean mass, and mood scores, but one thing stood out pretty clearly to me was the hormonal changes.

Specifically, his thyroid hormones (T3 and T4) were of interest to me.

Here are the T3 values:

6 months before competition: 1.34
3 months before competition: 0.74
The week of competition: 0.67
3 months post competition: 1.62
6 months post competition: 1.17

And here are the T4 values:

6 months before competition: 78.49
3 months before competition: 54.38
The week of competition: 47.67
3 months post competition: 73.79
6 months post competition: 73.94

As you can see, his thyroid hormones fell with prolonged dieting and recovered when his calorie intake increased.

This is normal and to be expected, but it should signify to those who never take a break from dieting that you ultimately can’t be in a deficit forever. You need to give your body a break with maintenance periods.

Also, this should serve as a reminder that the best time to get your hormones tested is when you are not in a calorie deficit. If you do have them tested while dieting it may come across as though your thyroid is not functioning well when, in fact, it is just that you’re in a deficit and your body is responding accordingly.