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Body Fat, EA or Hormones

This is another excerpt from The Women’s Book, looking a bit at the cause of menstrual cycle dysfunction and, specifically, secondary amenorrhea.  Even more specifically it looks at the cause of that dysfunction as it occurs in exercising women.  Early theories revolved around body fat percentage although it would turn out that energy availability (EA) played a much larger role.

Some Definitions

Since this is a short excerpt from a much longer chapter, I want to define a few terms so it will make sense.

When a woman is menstruating “normally” this is called eumenorrhea (“eu” = good).  In contrast, the lack of a menstrual cycle is termed amenorrhea.

Primary amenorrhea is when the onset of menstruation (called menarche) is delayed.  As frequently as not this occurs in females involved in sports such as gymnastics, ballet, ice skating and other sports that “emphasize thinness” (as the literature puts it).  Their intense training and dieting simply delay the normal onset of menstruation.

Secondary amenorrhea is the loss of the menstrual cycle that occurs in women after menarche has already occurred.  This can occur for many reasons but here I’m focusing on the amenorrhea seen in exercising women, an issue that started to occur more frequently as women started to really enter sport.

A related concept oligomenorrhea refers to an infrequency menstrual cycle, occurring every 35 to 90 days.

And yes this chapter addresses other related concepts, not just this one.Oligomenorrhea is an infrequent cycle, defined as a cycle occurring between 35+ and 90 days (the “normal” menstrual cycle runs from 24-32 days or so).  Hyperandrogenism refers to women with relatively higher testosterone than normal.

Body fat, Energy Balance or Hormones

As I mentioned above, it was originally thought that some critical level of body fat was required for a woman to start menstruating. Nobody knew why this was the case, it was just an observation. The idea was simply that until she had enough body fat to safely become pregnant and carry a baby to term, her body would not become reproductively active and there is certainly some logic to that.

This was before the discovery of leptin so nobody really knew why this case the case even if we know now that until leptin hits a certain level, reproduction will not start (1). It’s interesting to note that in recent years the average age of the start of menstruation has gone down (girls are starting earlier) and at least part of that is thought to be related to increasing levels of body fat in children. They are hitting whatever critical point earlier in life.

Because of this observation, it was basically assumed that the system worked in the opposite direction, that when women dropped below a certain level of body fat, that was the trigger for them to lose their menstrual cycle. Given that amenorrhea was often seen in sports which require body fat to be lowered and which place a primacy on thinness (for either performance or aesthetic reasons) this seemed completely logical. It just happened to be wrong.

Female endurance athletes were frequently found to have lost their cycle and usually had a low body fat. Female physique athletes, due to the nature of their sport, often have the same issues. All of this seemed to implicate body fat per se as the problem and many still think this is true. And while body fat level does have an indirect effect but it’s not the level of fat per se that is the issue.

As I mentioned above, it was also long assumed for the longest time that oligomenorrhea and amenorrhea were just different degrees of the same situation but this no longer looks to be the case. The hormonal profile is different, the cause appears to be different (the hyperandrogenism that goes along with certain types of sports and the women that pursue them) and this means that the treatments will be different (2). Once again, the hyperandrogenic oligomenorrheic may still be a in sport which requires them to lose weight/fat (i.e. weight class or some endurance sports) and the eventual loss of the cycle can still occur.

In any case, it was also found that female endurance athletes with roughly the same levels of body fat either did or did not maintain their menstrual cycle and body fat levels weren’t an absolute determinant of whether or not a female lost her cycle or not. The normally cycling women did show what looked like subclinical effects on their menstrual cycle but it was still present. For whatever reason, they had escaped the loss of their cycle despite being of similarly low body fat levels.

Other studies found the same with the menstrual cycle shutting down at different body fat levels. Certainly the problem was more frequently seen at low levels of body fat but there is a big confound here: to reduce body fat levels to the extremes requires a great deal of calorie restriction and exercise. And it would eventually be shown conclusively that it was not body fat per se but energy availability that was causing the problems (3).

Energy availability (EA) is defined as the differences between energy intake and exercise energy expenditure.  Basically it’s the calories that are left over for other biological processes.   So consider a female eating 1600 calories/day who is performing 400 calories/day of exercise.  She has an energy availability of 1200 calories. That is, her body has 1200 calories per day to allot to other biological processes.

And the basic idea is that, when those “left over” calories are limited, her body will have to prioritize some processes over others.  Since some are required for life and others are not, the relatively less important ones (such as reproduction) are reduced or shut down completely.  Since lean body mass (LBM) tends to be the most metabolically relevant aspect of physiology, EA is defined relative to LBM.  So if the female above has 120 lbs of LBM, her EA is 10 cal/lb LBM.

And through a variety of studies, research found that when a woman’s energy availability dropped below 9.6-13.6 cal/lb LBM (20-30 cal/kg) her system would be negatively affected. Levels of active thyroid (T3) drop quickly (although the threshold for this is a bit lower, about 11.3 cal/lb LBM) and LH pulsatility is lost along with a host of other adaptations. And, as would be expected, this is related to the rapid drop in leptin levels that occurs when women are in a caloric deficit (4).

In support of this cutoff value, studies of amenorrheic compared to normally cycling athletes show that the first group is consistently below 13.6 cal/lb LBM (30 cal/kg LBM) while the normally cycling women are above that. As well, even bringing energy availability even slightly above the cutoff value (i.e. to 31 cal/lb LBM or 14 cal/lb) by either decreasing exercise or increasing energy intake eventually restores the menstrual cycle.



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20 thoughts on “Body Fat, EA or Hormones

  1. Interesting to know …

    Also make sure that they catch “gone done” instead of “gone down” in “… the average age of the start of menstruation has gone done (girls are starting earlier).”

  2. So this is a spinoff of the women training & fatloss book, which was a spinoff of the best diet magnum opus…what’s the status of those projects? Us dudes are starting to feel neglected and no amount of “train better, eat less, and be patient” will convince us you’re not sitting on one or more magic bullets 🙂

  3. my daughter has elevated levels of testosterone. she was diagnosed with PCOS (polycystic ovary syndrome). an mri did not reveal cysts on her ovaries, and she is not overweight, which is how PCOS sometimes presents. she was not a hardcore athlete in middle school and ate a mix of healthy food and teenager junk food. she got her period briefly at 12, and then it came back once maybe at 13. something like that. she is now on birth control pills to regulate her hormone levels. she has a little bit of above normal hair growth on her stomach. she puts on muscle easily. i her mother put on muscle easily as well and gain weight in my abdomen, but i never had irregular periods or fertility problems. i think my daughter’s hormonal problems may be related to bpa exposure. even though i breast fed until she was 10 months old, later she had milk in a plastic bpa bottle warmed up in the microwave. in 2013 i believe bpa was removed from baby bottles. i also ate a lot of canned beans when i was breast feeding, so she could have gotten bpa that way as well.
    i want to discuss having her move off of bc pills and try metformin to reduce testosterone levels and use a nohormonal iud for birth control as i have many breast cancer risk factors, and so she may as well. so the less exposure to estrogen she has in the form of birth control pills the better. my daughter is 17 and muscular with a flat stomach.

  4. Good post, Lyle.

    Hate to be a correction nazi, but just a heads up that in the final paragraph it says, “bringing energy availability even slightly above the cutoff value (i.e. to 31 cal/lb LBM or 14 cal/lb)…”

    I believe the “31” should be “13”.

    I look forward to the book.

  5. Actually it’s a typo but not in exactly the way you suggest. 31 is the right number, my units are wrong as it should be 31 cal per KG LBM. Thanks for the catch in any case.

  6. While I will discuss PCOS in this book I am not discussing babies, kids or girls who are still developing. Above my paygrade and too many problems that can occur although BC is often used to normalize things. Best discussed with a primary care provider.

  7. No, this started life as a section in the magnum opus but is what the women and fat loss book was originally going to be. And men need to learn patience. Compared to what women deal with, that’s pretty much it.

  8. Typo:
    This was before the discovery of leptin so nobody really knew why ***this case the case ***even if we know now that

    I guess it should read, “this was the case”

  9. “While I will discuss PCOS in this book I am not discussing babies, kids or girls who are still developing. Above my paygrade and too many problems that can occur although BC is often used to normalize things. Best discussed with a primary care provider.”

    my daughter is under the care of a doctor. problems in adulthood often have their roots in fetal development on up. so it would seem solving this kind of problem would require a deeper understanding of the root causes which happen during a girl’s development- but which you don’t feel qualified to delve into. any qualified people or studies re fetal development and hyperandrongenism you could point me to?

  10. Sure, plenty of work on this. I talked about it briefly over a decade ago in one of my books. But I don’t see how it’s relevant to determine what happened in utero. The problem is the problem now; worry about dealing with it now. If your daughter has hyperandrogenism, it should be treated as such. But for girls who are still developing, it’s best handled by her doctor.

  11. “But I don’t see how it’s relevant to determine what happened in utero. The problem is the problem now; worry about dealing with it now. ”

    in cases in which treatment is not working or an individual doesn’t fit into typical types of , say PCOS, clues may be found in the history of the pregnancy and early years of development. Learning disability diagnosis, for example, depends on knowing any abnormalities that happened during the pregnancy. my exposing my daughter to high levels of bpa may affect her treatment in a way that is different from the typical PCOS case. but i have to find more info. i am planning on taking her to someone in the u of penn system (adolescent endocrinology) to hopefully get a higher level of expertise than can be provided by my ob/gyn (who put her on a triphasic bc pill with an average dose of 0.75 mg of norethindrone (a type of progestin) which i have since learned has been linked to have more than tripled the risk of breast cancer in women 20-49 years old.
    – for those interested see: “Recent Oral Contraceptive Use by Formulation and Breast Cancer among Women 20 to 49 Years of Age” in the journal Cancer Research 2014;74:4078-4089.

    “But for girls who are still developing, it’s best handled by her doctor.” in order for me to have confidence in the doctor, i need to be well-read on the subject first because a parent loves their child more than a doctor ever could.

  12. Looking forward to the book!

    Is a calorie a calorie in the case of energy availability? (I’ve heard some talk about carbohydrate being critical for cycling to begin again…)

  13. Don’t take this the wrong way but I think you’re looking for a problem where it may or may not not exist. You can theorize about what may or may not have happened during your pregnancy and there’s no doubt it plays a role. With about a billion (+- a billion) different contributing factors that you don’t know about.

    What is leading you to the belief that it is an atypical case of PCOS in the first place? etc, etc. If they aren’t responding to the therapy, of whatever sort, the doctor should change it or do more tests to better pin down the cause. But I think you’re looking for zebras where there may only be horses.

  14. Yes ish. Certainly carbs and fats will play a larger role energetically than protein but dietary fat has it’s own role in the whole cycle issue (needing to be above a certain level). I can’t see any case where one would be increased in lieu of the other under most situations anyhow. When I talk about “fixing” amenorrhea, I will basically approach it from the standpoint of getting across the critical EA threshold first, getting dietary fat above the thresehold, and the rest can come from carbs.

  15. My wife had hers stop after significant body fat gain. We have both used rfl this year and have lost almost all that we gained. Recently her cycle came back and has been perfectly regular. Is this a similar mechanism but rather than being too thin causing the issue being overweight is somehow lowering EA?

  16. Great excerpt, Lyle.

    As a weight class athlete, I’ve struggled with oligomenorrhea on and off over the years, so this particularly resonated with me. I’ve read some of your other articles on the female body, but I’d be lying if I didn’t say I wish there were more information available that is specifically about us ladies.

    I’m excited for a comprehensive guide to womens’ physiology (at least in regards to exercise and nutrition) to soon be available for purchase. I will be buying this as soon as it’s published!

  17. Ken, both a low EA and gaining a lot of body fat (obesity) can cause the cycle to be lost (although there may be an additional underlying cause such as PCOS with obesity). In the first case, calories have to be raised to “Fix” the problem. But frequently fat loss in the obese normalizes hormones. Infertility occurs more frequently in obese women and fat loss often normalizes the system. But it’s less to do with EA and more to do with what all happens with increasing levels of body fat and what happens when you reduce it. Congrats to your wife on getting it under control.

  18. Tomorrow is the third wednesday of July. Really looking forward to buy the book.

  19. And trust me that it’s nowhere close to being ready.

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