Intermittent fasting, exercise and women: what are the benefits?

I can’t open my podcast app, Twitter feed, or news alerts without seeing the mention of intermittent fasting. The benefits of dietary practices such as the 16:8 diet (eating within eight hours) are hailed by doctors, nutritionists and podcasters and are widely discussed among friends at dinner parties.

This kind of analysis of our diets isn’t new, but unlike other “tips” for eating faddy (looking at you, keto), intermittent fasting has a scientific basis. It seems to be the method the health world is obsessed with, in part because it doesn’t involve altering what you eat throughout the day.

The scientific findings are so compelling (like a 2016 paper that found IF to improve strength while reducing inflammation) that I’ve been tempted to try moving my dinner a little earlier and my breakfast a little earlier. bit later, reducing my meals into a shorter time frame. But I stopped trying intermittent fasting because, as someone who trains regularly, I’m especially aware of the importance of fueling up before training.

Experts have often advised me that pre-workout carbs boost performance and support hormonal health, so having a banana and an oatmeal latte before a morning workout has become non-negotiable.

However, for those who wish to shorten their eating window, is a longer break between dinner and breakfast a beneficial practice?

The benefits of intermittent fasting

“Essentially, when you fast, your insulin levels go down, your human growth hormone levels go up, and your cells also initiate very important repair processes, known as cellular autophagy. This means they metabolize and eliminate dysfunctional proteins that build up over time and cause damage,” says Holly Dunn, nutritionist and women’s health expert.

A woman making pancakes in the morning
Intermittent fasting is commonly practiced by skipping breakfast

“There are many potential benefits associated with these activities, from improving health to reducing the risk of developing neurogenic degenerative diseases like Alzheimer’s disease and even protecting against mental illnesses like depression.”

So what’s the problem ? The fact that virtually none of these studies were done on women, says Dunn. “Our hormonal cycle is an entirely additional system that influences everything, including our stress response, our immune system, and our metabolic profile,” she says. This means that we simply cannot extrapolate the research on metabolism and cellular function done in humans and apply it to us.

In fact, one of the only studies on IF that included women actually proved an opposite effect. A 2005 study showed that blood sugar regulation in women is actually worse after a 22-day period of intermittent fasting. “I think it’s quite interesting that the research done on women specifically conflicts with what we understand about the beneficial and metabolic effects of intermittent fasting,” Dunn says.

This doesn’t mean women shouldn’t fast – it just means we need to consider other factors, such as hormones, stress, and most importantly, exercise.

Intermittent fasting and exercise for women

This is a good time to note that biologically you are not fasting the moment you stop eating. As long as your body is digesting food, you are always in a “nourished” state. It takes hours to actually start a “fast”, hence why they tend to be so long (as in the 16:8 feeding style). But whether you accidentally exercise on an empty stomach by working out first with just black coffee to line your stomach, or intentionally don’t eat before exercising, there are significant implications for women.

For those who have a strong menstrual cycle that doesn’t fluctuate, prioritize sleep and recovery, eat enough throughout the day, and don’t have other health issues, Dunn says implementing of workouts and diets IF might be OK. The important point is that it’s probably not better for you.

A woman eating cashew nuts in a sports kit
If you exercise regularly, intermittent fasting may not be for you

“Exercise itself creates some of the same beneficial effects as intermittent fasting — for example, it improves insulin sensitivity and it can upregulate autophagy,” Dunn says. “But the latest research has shown that there is no added benefit to fasting and exercising. You are no more supporting your insulin levels than if you had just done either. And really, in this scenario, the question is whether you’re just adding extra stress on the body by not eating properly.

Low energy availability and relative energy deficit in sport (RED-S) are issues that, anecdotally, are becoming more common – perhaps because we need to apply mainstream sports science research performed in men to us as women. But as Dunn mentioned earlier, we have hormonal profiles that require a lot more consideration.

“Fasting increases sympathetic nervous system activity, adrenaline and cortisol production, stress hormones, excretion of the hunger hormone grehlin, and reduces glycogen stores. If you do this regularly alongside to a lot of stressful exercise, it can be a perfect storm for your hypothalamus – the hormonal center of the brain.We can link this huge influx of stress to adrenal dysfunction, burnout and reproductive hormone issues. feminine.

What if you practice IF but exercise after eating? “The jury is still out, but from the research, we know that the distribution of energy throughout the day is important,” Dunn says.

“Any period of what we call a micro-energy deficit, so a fasting window or altered or disrupted energy distribution, is linked to an increased susceptibility to hypothalamic amenorrhea – a hormonal dysfunction that causes rules.

“We know that how women eat and how they distribute that energy intake throughout the day is really important. The research was not done specifically with an intermittent fasting model, but it has been observed that female athletes who delay their food intake often have reproductive health and cycle regularity.

We know very well that every woman is different and that there is absolutely no one size fits all. Some research suggests that people with PCOS benefit from fasting, and Dunn points out that there are times in our cycle when we can benefit more than others.

“There is limited evidence to suggest that the second half of the cycle is not a good time for fasted training, as we already have a reduced ability to access carbohydrates for fuel. Those who are sensitive to a long cycle or an irregular cycle may want to avoid fasting before ovulation increases their risk of disruption of what is called the luteinizing hormone pulse, which could also be problematic.The answer is that there is no answer Absolute,” she says.

Should you exercise and do SI?

Clearly, research, headlines, and social media posts have ignored the complexities of combining intermittent fasting with a tough workout regimen, especially for women. As always, it’s not as simple as what people (even experts) share on Instagram.

“I’m definitely not of the opinion that women should ever do both together. But there can be issues if these two things are done chronically and we have to look at the whole person – what is their total stress load and life load? What does the rest of their diet look like? Dunn asks.

If you want to practice IF while exercising or just find that you’re only hungry for a short period of the day, Dunn recommends focusing on recovery and minimizing stress the rest of the day. . “For women, being aware of some of the warning signs of your diet and exercise routines, like feeling exhausted and poor recovery after exercise, means you know when you’re overdoing it” , explains Dunn.

There are also times in your life when you may not want to combine these practices, such as when you are going through a lot of work, family, or personal stress, or when you are training for an event that requires more exercise than the normal. And, as always, don’t take everything at face value – in the pursuit of optimal health, we can often have too much of a good thing. For now, I’m writing off my IF curiosity in favor of the workout routine I love.