Thanks for your good question. Let me start to answer your question by saying that, most of time, it is wrong to blame "funny periods" on exercise. I call this the "Myth of Athletic Amenorrhea"
To blame women‘s "funny" periods (oligomenorrhea if cycles longer than 35 days) or absent periods (amenorrhea meaning no flow for six or more months) on too much exercise is usually just prejudice against women. However, this notion persists in our culture even though it has been shown to be wrong by three different studies (1-3 [1]). This notion of women's exercise causing funny periods is a way of saying something that we as a culture have stopped believing-women shouldn't be athletes but instead should be Victorian wallflowers!
If I don't think that exercise is causing your periods to be long and unpredictable, why are they? First, we have to understand the complex control of women's menstruation and ovulation. Women's reproduction is carefully controlled in favour of survival. This is because it requires energy to menstruate, to ovulate and make progesterone (which requires more calories because it increases our basal temperature) and finally because getting pregnant is an even further drain on our body's resources.
Women's menstrual cycles and ovulation are carefully controlled by our hypothalamus in the brain. The part that is the "mastermind" gets information about how much we are eating, how much energy we are expending, how stressed we are and whether or not we are ill. Also, it takes about 12 years after the first period for the coordination of this complex reproductive system to "grow up" and our menstrual cycles to become regularly ovulatory.
I suspect that the stress of school and your relatively young gynecological age (meaning how many years it has been since your menarche) are enough reason for your current menstrual cycles to be far apart. After all, if your first period was at 12 or 13 years old, as is average, you have had only 6-7 years for this essential maturation of reproduction.
Another possible reason for oligomenorrhea is that your weight is slightly lower than normal (BMI 18.5-24.9 is ideal). It also sounds like you may be concerned about gaining weight. Although I totally agree that over-eating can make you feel sluggish and fat, being too careful can also be another kind of stress called "cognitive dietary restraint." Dr. Susan Barr, a professor of nutrition at UBC, and I have shown in multiple studies that this kind of concern about "over-eating" is likely to cause irregular cycles in younger women, and regular cycles with ovulatory disturbances in those who are gynecologically mature (4 [1]). In that study we showed that those with "eating restraint" had higher cortisol levels indicating that making decisions about what to eat or not was stressful. We also have shown that not ovulating normally, even if the menstrual cycle seems to be normal, is a risk for more rapid bone loss.
Ok-the bottom line about what you can do. First of all, you need to get to know yourself a bit better by tracking your menstrual cycle. Here on the CeMCOR website you can watch video clips about how important it is to understand and value your own menstrual cycle [2]. You can download the Menstrual Cycle Diary [3]© and track your experiences. Your period is likely to be on the way when you notice some breast tenderness or stretchy vaginal mucus. Just keeping this kind of a record and being able to discuss what you're learning with someone else (a friend, your mom, your family doctor) appears to help your cycles improve.
Secondly, I'd continue to do your exercise for the same amount of time but substitute some weight training for a few of your running sessions a week. And gradually become aware of whether you are eating more when you do more exercise-if you are not, your hypothalamus will be warning your reproductive system that it's not ready to be regular and ovulatory.
In the mean time, I'm a bit concerned because your low weight and irregular periods mean you're not building optimal, strong bones right now. To compensate, I'd make sure to get enough calcium (from milk, yogurt, cheese or fortified soy or rice beverages) so that you have a serving with every meal plus take a multiple vitamin and a calcium pill (say 500 mg elemental calcium) at bedtime. Also, for now, I'd suggest that you take a 1000-unit vitamin D pill a day. For more information about the things that prevent osteoporosis in young women see "The ABCs of Bone Health for Premenopausal Women" [4] [PDF] remembering that the extra vitamin D and calcium are needed until your periods are regular and ovulatory.
Finally, when you are ready, and with healthy food, I'd gradually let your weight increase by a pound or two. As you gain confidence you will see that you don't need to have such a low weight to feel and look good.
Hope this is helpful for you,
All the best,
Jerilynn
- Rogol AD, Weltman A, Weltman JY, Serp RI, Snead DB, Levine S et al. Durability of the reproductive axis in eumenorrheic women during 1 yr of endurance training. J.Appl.Physiol. 1992;72:1571.
- Bonen A. Recreational exercise does not impair menstrual cycles: a prospective study. Int.J.Sports Med. 1992;13:110-20.
- Prior JC, Vigna YM, Schechter MT, Burgess AE. Spinal bone loss and ovulatory disturbances. N Engl J Med 1990;323:1221-7.
- McLean JA, Barr SI, Prior JC. Cognitive dietary restraint is associated with higher urinary cortisol excretion in healthy premenopausal women. Am.J.Clin.Nutr. 2001;73:7-12.
