Hormonal Changes During Bikini Prep (What’s Normal — and What Isn’t)
This post is part of The Ultimate Bikini Prep Guide – check out the full guide for more!
One good trend I see in bodybuilding is the number of people I see who come to me looking for a coach, but asking questions and wanting to be mindful of maintaining proper hormonal function during a prep. I think this is a sign that people are reading cautionary tales from other competitors and taking it to heart.
That being said, having a prep where you actually hit the mark in terms of conditioning while maintaining proper hormonal levels is going to be a mutually exclusive thing for a lot of women.
The real key is, if you do experience some dysregulation, how do you know and what do you do about it?
Prep Is a Physiological Stressor — Not Just a Diet
Once you go through a prep start to finish you realize how true this is – it’s a whole body thing, which includes your brain (mental health), gut (digestive regularity) and more.
The diet is part of it, but it’s the big picture of total stress that prep places on your body that ends up being the problem here.
I think in America especially in 2026, we equate stress with “busy” which, let’s be clear, I think we’re pretty much ALL busy ALL the time.
Stress also means overworked and under recovered, both of which are things that prep and the overall bodybuilding culture at large actively encourage.
What Actually Changes Hormonally During Prep
There are a lot of hormones in the body and they all tend to “do things” during prep.
Testosterone, estrogen, thyroid, ghrelin, leptin, and insulin all play huge roles in the quality of your prep and they’re all directly impacted by your behavior in prep on a daily basis.
Thyroid and metabolic output
Your thyroid gland regulates your body’s metabolism, and a healthy, active thyroid keeps metabolism at a healthy rate where fat loss can happen in somewhat predictable ways. For people with reduced thyroid activity (hypothyroidism), this is a problem – although treatable with prescription thyroid meds.
Prep stress puts the body in a sympathetic state where it’s feels under attack or at risk – and our evolutionary response to high stress (think primitive humans having to hunt for food and possibly being unsuccessful – high stress) is to downregulate your metabolism as a survival technique.
In prep, we know where our next meal is coming from (though it’s never as big as we’d like it to be), but the same metabolic downregulation while in a deficit still happens. This is largely unavoidable and, as they saying goes, it’s a feature of the human body rather than a bug.
Reproductive hormones and libido
Your testosterone and estrogen will tank, which reduces sex drive and can also impact performance in the gym, sleep quality, energy level/output, and overall rate of progress as well as your ability to retain muscle in a deficit.
Obviously, all of that is problematic.
Cortisol and stress tolerance
Cortisol is a catabolic hormone (muscle wasting) and by that alone we know it’s important to manage it and keep it under control, but we have to do so in an environment (prep) that is designed to drive it up.
Managing your stress and recognizing the signs of cortisol overload becomes absolutely critical.
Hunger signals and satiety
Ghrelin and leptin are responsible for regulating appetite and energy balance. Think of ghrelin as the hunger hormone, and leptin as your satiety hormone. Throughout prep, the former elevates and the latter drops – and ghrelin in particular can be slow to move. This is why a lot of people are fine with caloric drops earlier in prep and then also can’t stop eating even 6-8 weeks after the show – their ghrelin is just out of control.
Leptin is also produced by your adipose tissue so as you lean out, there will be less of it present in your system. This is one thing you really can’t control.
What Do We Do About It?
The main thing I stress is to be aware of these changes and how they can impact your prep. Make sure you’re tracking things like training quality, sleep, blood glucose, sex drive, etc – those will give you leading indicators if something is starting to float out of range.
A fairly universal approach for all of these is to interrupt the deficit with periodic refeeds – although the duration and size of those refeeds really matters.
What’s Normal vs. What Deserves Attention
To be clear, ALL of this is normal. A lot of it (hunger, etc) just comes down to the mental ability to shut it out and not worry about it.
Thyroid and sex hormones are the ones that will have a direct impact on the process of your prep so it’s more important to keep those in a happier range. For women this means – in ideal circumstances – maintaining cycle regularity, although for some women that simply won’t happen. One’s sensitivity to cycle disruption is VERY individual, I’ve worked with women who can be starved and perform a mountain of cardio and maintain their cycle all the way to show day, and others still who miss it after one moderate week in prep – though the latter is very rare.
Why the Margin Shrinks as You Get Leaner
One of the key things working against you here is time – the margin shrinks because the calendar becomes less forgiving. The mitigation strategies that we have at our disposal all require time (refeed = time not in a deficit = time not leaning out) and if you didn’t plan for that on the front end you can end up in hot water.
Also as some of these hormones become dysregulated it becomes a little harder to show up as the best version of you each day, and your training/cardio intensity can drop off which will produce a less great result also.
What Happens After Prep?
The great news here is that all of this stuff corrects itself in time when you return to normal, assuming you do, in fact, return to “normal” after your show. This is easier said than done as the desire to binge eat like a mofo runs rampant, and while in the short term that will improve things it will cause further dysregulation and skewing if allowed to continue.
Go into prep with a plan for how to handle things AFTER the show as well. When you’re 1-2 weeks out, work with your coach (or on your own) work up your post-show diet and make sure you’re ready to hop on that within 1-2 days after the show.
Be ready to white-knuckle the diet for a bit. The desire to just GO ALL OUT and eat will be strong and remain strong for as long as it takes for your ghrelin to regulate back to normalcy.
Sex hormones will return to normal following a standard diet (overdoing it may actually cause further suppression), leptin and thyroid will rebalance fairly quickly.
Your main goal post-show is actually just to regain the body fat stores you need to allow all of these marker to return back to normal naturally.
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