By Dr. Amy Shah, MD
Chances are if you are health and fitness savvy, you’ve heard of intermittent fasting and its benefits for fat loss and overall health.
But did you know that, if you’re a woman, fasting could lead to hormonal imbalance and could lead to fertility issues? Here, we’ll discuss the best ways for women to enjoy the positive aspects of intermittent fasting without putting their health at risk.
An intermittent fast is a brief fast where, for 12–16 hours or more, you don’t eat anything except water (a few exceptions apply). And while that may sound incredibly difficult to achieve, you might already be fasting without knowing it if you eat dinner at, say, 7 p.m. and break your fast in the morning between 7—10 a.m. — and if you only have water and black coffee or tea between.
For others of us who have been trained to eat six times a day to “keep our metabolism up,” it can be an arduous and seemingly contradictory feat to go 12-plus hours on water alone. But science actually backs this ancient practice.
Medical studies have shown that intermittent fasting:
- Increases energy
- Improves cognition, memory and clear-thinking (1)
- Makes us less insulin resistant, staving off fat and insulin related disease by reducing levels of circulating IGF-1 and increasing insulin sensitivity without lowering the resting metabolic rate (2)
- May improve immunity, lower diabetes risk, and improve heart health (3)
- Increases production of brain neurotropic growth factor — a protein that promotes neuron growth and protection — making us more resilient to neurological stress and thus staving off neurodegenerative diseases (4)
My Initial Fasting Experience
Knowing the potential health benefits of intermittent fasting for women, I was eager to give it a try. Unfortunately, I failed MISERABLY at my first attempt. Let’s just say I did NOT experience increased energy and clear-mindedness.
The first day I under-ate and couldn’t sleep for hunger pangs. The next day, tired and cranky, I overate with the veracity of a starved animal. That’s when my hunger and hormone roller coaster began. And after one full week of this, I had to quit.
As a physician I wondered if other women had experienced something similar. And when I searched the internet, I discovered that, across message boards, blogs and online communities, women were complaining about intermittent fasting and its effect on their hormones. In fact, there was scientific literature that supported all of our experiences.
The Fasting and Hormone Connection
To put it simply, intermittent fasting can cause hormonal imbalance in women if it’s not done correctly. (5) Women are extremely sensitive to signals of starvation, and if the body senses that it is being starved, it will ramp up production of the hunger hormones leptin and ghrelin.
So when women experience insatiable hunger after under-eating, they are actually experiencing the increased production of these hormones. It’s the female body’s way of protecting a potential fetus — even when a woman is not pregnant.
Of course, though, many women ignore these hunger cues causing the signals to get even louder. Or, worse, we try to ignore them, then fail and binge later, then follow that up with under-eating and starvation again. And guess what? That vicious cycle can throw your hormones out of whack and even halt ovulation.
In animal studies, after two weeks of intermittent fasting, female rats stopped having menstrual cycles and their ovaries shrunk while experiencing more insomnia than their male counterparts (though the male rats did experience lower testosterone production). (6) Unfortunately, there are very few human studies looking at the differences between intermittent fasting for men and women, but the animal studies confirm our suspicion: Intermittent fasting can sometimes throw off a woman’s hormonal balance, cause fertility problems and exacerbate eating disorders like anorexia, bulimia and binge eating disorder.
But there is a solution …
Crescendo Fasting for Women
Intermittent fasting for women can be hard on your body if you are new to it or if you jump in too quickly. So if you are a woman or trying fasting for the first time, you might benefit from modified — or crescendo — intermittent fasting.
Crescendo fasting only requires you to fast a few days a week instead of every day. My experience is that women get a lot more benefit from doing it this way without accidentally throwing their hormones into frenzy. This is a more gentle approach that helps the body more easily adapt to fasting. And if women do it right, it can be an amazing way to shave off body fat, improve inflammatory markers and gain energy. (7)
Not all women need crescendo fasting, but it will ensure success in most.
Rules of Crescendo Fasting:
- Fast on 2–3 nonconsecutive days per week (e.g. Tuesday, Thursday and Saturday)
- On fasting days, do yoga or light cardio.
- Ideally, fast for 12–16 hours.
- Eat normally on your strength training/HIIT workouts intense exercise days.
- Drink plenty of water. (Tea and coffee are okay, too, as long as there is no added milk or sweetener)
- After two weeks, feel free to add one more day of fasting.
- Optional: Consider taking 5–8 grams of BCAAs during your fast. A branched chain amino acid supplement has few calories but provides fuel to muscles. This can take the edge off hunger and fatigue.
If you have failed at intermittent fasting before, try this crescendo style for a better, more sustainable experience — especially if you are a woman.
Amy Shah, M.D., is double board-certified doctor who received her medical training from Cornell, Harvard and Columbia Universities. She has a thriving medical practice in the Phoenix area, where she sees more than 5,000 patients each year. In 2015, Dr. Shah was named one of the “Top 100 Women in Wellness to Watch” by MindBodyGreen and was a guest on the Dr. Oz show.