Lost your period? You might just need to eat more. A lot more. Losing your period to undereating is called hypothalamic amenorrhea and is common, especially in women under thirty.
Hypothalamic amenorrhea is sometimes misdiagnosed as polycystic ovary syndrome (PCOS) because both hypothalamic amenorrhea and PCOS can present with “polycystic ovaries” on a pelvic ultrasound exam.
3 signs of undereating and hypothalamic amenorrhea
If your missing period is due to undereating, you will have one or more of the following:
- no withdrawal bleed from the pill or a progestin-challenge
- low fasting insulin (less than 4 mIU/L or 25 pmol/L)
- low luteinizing hormone (LH).
You could also have polycystic ovaries (or not). Read Is it PCOS or hypothalamic amenorrhea?
How undereating stops periods
Too few calories or too little of any macronutrient (including carbohydrate) can switch off the signalling of the hypothalamus to the ovaries. It’s not a malfunction but is instead the brain making the smart decision to avoid pregnancy when there is not enough food to make a baby. It’s also called relative energy deficiency which is the ratio between energy intake, body mass, and energy expenditure (exercise).
Hypothalamic amenorrhea is like an ovulation “off switch.”
Men do not have a similar “off switch” because although the male hypothalamus can dial testosterone up and down, it would never turn testosterone off completely. Why? Because a male hypothalamus never has to worry whether there will be access to the 75,000 additional calories it takes to grow a baby.
Ovulation can be switched back on by consuming more food and aiming for a daily intake of at least 2500 total calories and 200 grams of starch. With increased calories and starch, ovulation should resume within six months. It takes that long because of the “100 days to ovulation” I describe in Period Repair Manual.
👉 Tip: Hormonal birth control is not an effective treatment for hypothalamic amenorrhea because pill-bleeds are not periods.
Ovarian set point
But what about that friend who did a keto diet and did not lose her period? Hypothalamic amenorrhea is more likely to occur in some women compared to others which may depend on ancestry. Evolutionary biologist Grazyna Jasienska explains in her book Fragile Wisdom that different women have different “ovarian set points,” which means different requirements for food energy to be able to ovulate.
Energy is the key to understanding ovarian function. ~ Dr. Grazyna Jasienska
Do you have an eating disorder?
If you’re frightened by the idea of eating more, please consider whether you have an eating disorder. Approach it with self-love and self-forgiveness, and know you’re not alone. Eating disorders are common and nothing to be ashamed of.
Reach out for help.