For the last few years intermittent fasting (IF) has been gaining momentum to the point that it is commonplace for many people that I see as clients as well as being documented in popular media to do with health, nutrition and fitness. It is a rare day I spend in clinical practice where at least 1 or 2 of my clients are not either already doing IF when they come to see me or are asking questions about it. There is a plethora of information on the web about it, including this brilliant article, but what I wanted to do in this post was to draw your attention to a few things you may not have considered about it or misunderstood in how to partake in it.
First thing is, the majority of research on IF has been done on men, not women. As much as we like to clump ‘all’ individuals together, when talking nutrition it is becoming clear in the last decade that maybe we don’t react the same and we really need to be doing studies that pull apart the statistics between how women and men respond to certain dietary protocols as a separate category rather than just looking at how they group responded. Most of the IF research has not even included women in their studies so that also leaves a bit of a gap in information as to how a woman’s body responds to a long term energy restriction.
You see, men’s and women’s bodies do not react the same under similar ‘stressful’ situations, and this at times has not been taken into account. The research that has been done on female rats is also pointing to detrimental issues with IF for females where as the male rats are responding in a favorable light. Don’t get me wrong, fasting has been shown to have positive benefits in BOTH sexes for cancer, brain and again health but when it comes to the female reproductive system this is where the problems start to show up.
When female bodies are put under ‘stress’ from under eating or calorie restriction it is likely that we trigger a cascade of hormone reactions where the body panics that there may not be enough food to sustain ‘two people’. This leads to breaks on our reproductive system so that it doesn’t have to chose to be supporting more than one person with the available food quantities on offer. Now I know I am over simplifying the situation and female bodies are capable of energy restriction but I am just wanting to point out that possibly how the popular media is suggesting we ALL fast or IF may not be the best way for both sexes, or even certain sexes at different stages in life, to go about it.
There are scientists and researchers saying, yes women are more sensitive to this so we may want to adapt the options. Instead of doing a 20/4 or 16/8 IF where you have a long window of fasting and a short window of eating, which may not be the best for the female body, they are offering the idea that women could adopt a 12/12 IF. That is a BIG difference from a 16/8 but if it will help preserve a females monthly cycle and not compromise their reproductive health I am all for this ‘softer’ approach. I also want to point out that a females monthly cycle is not just important for fertility but it is vital for bone health as well as some resulting in down stream consequences to the thyroid and metabolic health.
So how should women go about IF if they want to give it a try? I love the idea of trying the 12/12 as it limits the time one is ingesting food over the day but not so much to put the body into a panic that it is starving. I am also a fan of everyone eating properly after exercise in the morning and not continuing their fast beyond that as it will potentially compromise glycogen replacement, energy levels and your immune system. I personally feel that women NOT doing large amounts of training fasted is a wise idea. Yes, yes I know its all the rage to do fasted training to increase metabolic flexibility and enhance fat burning but we have potentially taken this too far and I find many of my clients doing ALL their sessions fasted rather than just 2 or so recovery sessions per week in that manner. If you (male or female) are doing HIIT training, intervals or weights its is mainly fueled by carbohydrates and you may get more out of your training session and feel better the WHOLE session if you have a small snack of carbohydrate before you head out. Dr Stacy Sims who wrote the book Roar suggests in her book that women should not train fasted and should consume a small amount of carbohydrate or protein (or even just BCAA’s) before training.
I would also like to suggest, that no matter if you are male or female (as far as natural hormones go) you should also just check in with yourself and how your body feels with eating, IF, fasted or non fasted training. We are so keen to read about what to do and how to do it in nutrition and sport that we forget to check in with ourselves and how our body is feeling/responding and to listen to the signals it is sending us.
If you are doing any form of IF (be it alternate day fasting or shorter window of eating etc) if it is changing your reproductive cycle for the worse, your energy levels are less or certain physical symptoms such as compromised immune system, skin or hair changes occur then may need to reconsider. Those indications to the limits you are setting is your body is telling you that is it too much. Our body is so much smarter than we give it credit for, please stop and listen for a change.