Can Training Shut Down your Reproductive System? (i.e. cause no periods / low testosterone in men)

DDT Nation! Today we have a fantastic guest post by our friend Nicola Rinaldi who is an author and has a PhD in computational biology. We’re excited to have her talk about how the reproductive system can shut down in 5 key ways. Specifically for women that lose their periods and for men’s testosterone levels becoming low. We see this a lot in competitors and those that are on very restrictive diets for long periods of times so we wanted to educate you on how to avoid this and what red flags to look out for.

Without further ado, let’s learn about how our reproductive system shuts down and what to do to mitigate it.

– Chris and Eric


The short answer is yes. That probably doesn’t surprise you all that much, “everyone knows” that Olympic level athletes or women training for marathons or bodybuilding competitions tend to lose their periods. What might surprise you is that while it is true that hours a day of exercise can play a part in reproductive shut-down, a much lower amount of exercise can have a similar effect, particularly in combination with other factors.

Side Note: It’s important to note that reproductive shutdown occurs in both genders. In women a missing period is easy to detect (unless on birth control); in men lowered testosterone and other effects are much less obvious but still detrimental.

In my ten years of research on this subject, I have found that there are five factors that are involved in suppressing reproductive function:

  1. restrictive eating (intentional or not)
  2. exercise
  3. stress
  4. weight and/or weight loss
  5. genetics

Any one of those, taken to an extreme, can cause missing periods/low testosterone, but generally it is a combination that is the culprit.

There was an interesting study done in monkeys illustrating the synergy that takes place [1]. Three groups of monkeys were exposed to different conditions:

1) exercise with mild food restriction

2) stress (a change in housing environment) or

3) both exercise/food restriction AND a cage move

A couple of monkeys exposed to either 1 or 2 skipped their periods, but eight out of ten in the exercise plus stress group had abnormal/missing cycles. So the effects were more than additive: synergy. The combination of exercise and undereating with stress did a number on the monkeys’ reproductive systems, and the same effect seems to occur in humans.

But first, let’s talk about each factor separately.



Restrictive Eating

We’ll start with restrictive eating. This comes in two forms:

1. Under fueling, as in not eating enough calories to supply energy for all daily needs. This plays a major part in shutting down the reproductive system because when the body is lacking energy it has to conserve where it can, and reproduction is non-essential [2]. The functions that are essential, like pumping blood, energizing the brain, breathing etc., take top priority and use a surprising number of calories (which vary a lot depending on body size and composition). On top of that, the body expends energy to fuel muscles during normal daily movement (e.g. walking from bed to bathroom, to get food, moving food to mouth). Then there’s the energy used by planned exercise. If one is intentionally restricting calories, or even unintentionally under fueling, this alone can shut down reproduction.

2. The second component to restrictive eating that can equally play a part in suppressing reproduction is restriction of food groups and macronutrients. It is common these days, especially among athletes or those wanting to “lean up” quickly, to eat a low-carb diet; in previous decades like during my formative years, we were told to avoid fat as much as possible. However, the different types of nutrients you consume are all sensed by parts of your digestive system, which send out hormonal signals indicating to your brain (specifically a part called the hypothalamus) both what and how much you’ve eaten. Glucose and insulin increase upon carbohydrate intake, PYY upon fat intake, and CCK after protein (along with many others bu t you get the picture [3].) These hormones are sensed by the hypothalamus and play a part in keeping it active, or alternately, if the signals are not received, some paths in the hypothalamus are shut down. And depending on how many paths are turned off, the hypothalamus may or may not send the downstream signals to the reproductive system.

Take home message: How much and what you eat can have a strong impact on your reproductive system. Make sure that you are getting sufficient calories for all your needs and also eat from all food groups as much as possible. Balance is key.



The next factor to discuss is exercise. As part of a book that I recently completed on the subject of missing periods and recovery (No Period. Now What?) I performed a comprehensive survey of 300 women who had missing periods (the technical term is hypothalamic amenorrhea, or HA). Many were hard-core exercisers, supporting the common understanding of what causes missing periods, but some hardly exercised at all. The median was an hour a day, six days a week, which really doesn’t seem excessive, does it? The graph below shows the distribution of time spent exercising with days per week of exercise, with the individual point in dark grey circles and the totals for each row/column in light grey.

These changes are important to make.


The detrimental effects of exercise have been noted in a few clinical studies: even in women who are having regular periods, exercise is associated with menstrual cycle abnormalities like no ovulation or a shortened luteal phase (the time between ovulation and a period) in about 50% [4,5]. Here too there are hormonal systems in play that can shut down the hypothalamus; intense exercise increases cortisol [6], which suppresses the hypothalamus. Especially in conjunction with restrictive eating, this means bye-bye period (or testosterone.)

Take home message: Intense exercise (even in relatively small amounts) can play a part in reproductive shut-down. If you are training for a competition or particular event, scale back on that training significantly after the event is over to allow your body to recover. Take rest days. Again, it’s all about balance.



The third factor is stress. And here we’re talking about psychological stress, not the stress of exercise (note that while exercise may feel like stress relief due to the endorphins, the cortisol that is generated is sensed by the body as stress). Mental stress also raises cortisol levels, which again, suppress the hypothalamus. Obviously acute stress like the death of a loved one, a divorce, and the like can wreak reproductive havoc, but so can the much less apparent chronic stress. This can result from general anxiety, work-related stress and other commonly recognized factors, but also the stress of following a rigid diet and exercise schedule. Do you feel anxious or guilty if you don’t follow your exercise plan or eat something you’re “not supposed to?” Do you spend hours scouring labels and planning meals? Are you a perfectionist? Living up to all those self or externally imposed ideals can be incredibly stressful, leading to chronically increased cortisol and reproductive shut down, particularly in combination with restrictive eating and/or exercise.

Take home message: Stress, from any number of sources, can either exacerbate or cause reproductive shutdown. The benefits of relaxing eating/ exercise rules and taking time for yourself will be immense. Again, Balance.



Weight Loss

A common misunderstanding (myth) is that a woman has to be anorexic or skeletal to lose her period. While many women with missing periods are on the lower side of the weight spectrum, that is not true for everyone by any means. The combination of factors above can cause missing periods regardless of BMI, although HA is more common at lower BMIs. This is partially due to low leptin and insulin levels associated with low body fat [7]. Also of interest is that the restriction required to lose significant amounts of weight (e.g. more than 10lb) seems to have lasting repercussions, making one more susceptible, perhaps, to loss of reproductive function (82% of my survey respondents had lost more than 10lb at some point in the past.) This may also be due to long term effects on the leptin system.

Weight loss to below ‘normal’ levels often needs to be reversed in order to recover missing periods, which comes along with reducing exercise and removing food restrictions as touched upon above. For those with non-working reproductive systems at higher than normal weights, after food restrictions and exercise habits have been adjusted, there are medications that can help to reset the hormonal system and restart things.

Take home message: Weight loss or a current low weight (typically a BMI below 22-23 for a woman) can make one susceptible to reproductive shut-down. Our society currently glorifies a physique—particularly for women, but also for men—that is not necessarily healthy in the long term, particularly for the reproductive system, but also for bones, brain, and heart. We encourage balance in this area as well.



The last factor is genetics, which can be dealt with quickly as I am definitely running long… There are a number of small changes in the hormones and hormone receptors involved in controlling the reproductive system that have been discovered in women with HA [8]. This is one explanation for why two people can seemingly have the same habits and yet one is ‘normal’ and the other experiences reproductive issues. Comparison is the thief of joy!

Take home message: This is one explanation for why two people can seemingly have the same habits and yet one is ‘normal’ and the other experiences reproductive issues. Comparison with others is pointless, you have to do what is healthy for YOU.

As you can probably tell, this is an extremely complex issue, and each case is unique. I have learned so much in the last ten years not only about the causes of hypothalamic amenorrhea, but also how to recover – and even further, how it can impact fertility and even life after pregnancy. I recently published No Period. Now What?, which goes into much greater detail and provides even more evidence on the science around missing periods (much of which it seems is in common with men, although much less research has been performed on the male side due to the lack of obvious symptomology), recovery, and additional avenues to pursue.

If you’re affected by a missing period, please check out the book and join our facebook group for support


Action Steps

In the meantime, some steps you can take today toward true health including a functioning reproductive system:

  1. Make sure to fully fuel your body for day to day activities AND exercise
  2. Incorporate balance into your exercise routines: take rest days, and if you’ve lost your period or been diagnosed with low testosterone, cut out high intensity exercise as you work toward recovery
  3. Examine what factors in your life might be causing stress (how much time do you spend each day thinking about food and exercise?) and find ways to mitigate those stressors
  4. Think about whether your current weight is healthy for your body, or are you having to work hard to maintain a weight that is “too thin for you”?
  5. Have balance with everything

In the end, what I have discovered is that the constant pressure to change bodies to conform to (often Photoshopped) societal ideals is wreaking havoc on both physical and mental health. Kindness to ourselves, exercising and eating for health and not because we believe our lives will be better if we are a certain size, keeping balance/moderation in exercise and eating: that is what will get each of us to the happiest version of ourselves.




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About Nicola:

Nico has a PhD in computational biology from MIT. After graduating she worked for a biotechnology company while pursuing her dreams of a family, which were thwarted by a diagnosis of hypothalamic amenorrhea (no periods). Eighteen months of trying to conceive followed. She spent hours on research, using the knowledge gained to work on recovery. Concurrently, she tried the medical route to pregnancy, with multiple doctor visits, injections, and ultrasounds resulting only in failure. Ultimately, she was able to achieve a natural pregnancy. Since that time, Nicola has shared her knowledge of the path to recovery, helping hundreds of others achieve their dreams of womanhood and pregnancy. She has spent the last three years as a stay-at-home mom, with her three boys, while writing this comprehensive guide to recovery.


twitter: @noperiodnowwhat

instagram: @noperiodnowwhat



















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[2] Wade GN, Jones JE. “Neuroendocrinology of Nutritional Infertility.” American

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[3] Tracy AL, et al. “Regulation of Energy Intake in Humans.” Endotext. Updated

Aug. 5, 2013.



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[6] Hill EE, et al. “Exercise and Circulating Cortisol Levels: The Intensity Threshold

Effect.” Journal of Endocrinological Investigation. 31(7) 2008: 587-91.


[7] Bruni V, et al. “Body Composition Variables and Leptin Levels in Functional

Hypothalamic Amenorrhea and Amenorrhea Related to Eating Disorders.”

Journal of Pediatric and Adolescent Gynecology. 24(6) 2011: 347-52.


[8] Caronia LM, et al. “A Genetic Basis for Functional Hypothalamic Amenorrhea.”

The New England Journal of Medicine. 364(3) 2011: 215-25.