Quick answer: Much exercise and fasting research has historically under-represented women, and doesn’t always translate to them. Fasting raises cortisol and can disrupt oestrogen, thyroid and other hormone levels — especially peri- and post-menopause — and many women benefit from eating something before exercising rather than training fasted.
I believe a key quality of a good doctor is to be humble. This can take many forms, but with respect to these coming posts, I mean the following. Humans, and doctors in particular in my experience, tend to become rather tied to their beliefs and convictions, especially as they get older. However, a good doctor should be able to appraise new data that gets presented to them, and consider whether they should change or modify their view on that topic. No-one likes to be wrong, but doctors will make mistakes. I have made mistakes, and will continue to do so. Having the self-awareness to acknowledge them, reflect, and improve is therefore super important.
Why mention that here? Well, when I do my research into a blog post, sometimes it makes me realise that there is a lot I didn’t know I didn’t know on a topic (I think it was Donald Rumsfeld who famously said this about terrorism intelligence!). In researching for the forthcoming posts on women’s health when it pertains to exercise, I think I was just plain ignorant about some things. I will also however say that so are many of the online ‘experts’ whose advice you might see. If I’m being educated, I hope you are too!
I have no financial or other conflict of interest in the health information I put out online, and have a degree in medical research from University College London, so you can be confident that my posts and online content is from the latest and best research.
You might be thinking, ‘well I don’t do much exercise so this isn’t relevant to me’ or ‘i’m a man so this isn’t relevant to me’ or ‘I go running/swimming/insert sport here every week so I’m all good thanks’. I hope to give you pause for thought over the coming weeks, there should be something here for everyone!
I’ve said before that women are consistently under-represented in trials. Too often I think it is assumed women are just the same as men. Funny how often when this is explored more deeply in medical research it’s found to be incorrect.
Why fasting research doesn’t always apply to women
So where to start? Let’s begin with food, specifically when to eat around exercise, and what effect intermittent fasting has.
Intermittent fasting, and time restricted eating are increasingly popular, and indeed practised routinely in some religions. My understanding has been that for many people this is a good thing – lower rates of diabetes, various genetic signalling pathways, insulin sensitivity and so on all improve. A recent Lancet paper (hugely respected medical journal) presented a meta-analysis (summary of many trials) on the subject. The paper ran to over 12,000 words. Guess how many of those words was ‘woman’?
8.
What happens hormonally when women fast?
Where women were mentioned, the results of intermittent fasting were not great. Hormone fluctuations in women are of huge importance. Fasting increases metabolic stress, and with it, the hormone cortisol rises. Cortisol levels fluctuate anyway throughout the day, being highest 30 minutes after waking. Not eating keeps these stress hormone levels higher, with knock-on effects on oestrogen, thyroid hormone and luteinising hormone to name three. Clearly this will vary also with a woman’s age and menstrual status. Women need fuel to tie in with their circadian rhythm, and this seems rather different from men.
The situation is worse if a woman exercises early without eating. In fact for women at any point in the day fuel is important before exercise – again – different from men (and I will go into more detail on this in future weeks). This problem only gets worse with age, particularly peri- or post-menopause.
My wife has historically not eaten breakfast, preferring a coffee and water. She is also peri-menopausal (I checked she doesn’t mind me saying!), and with that comes a variety of challenges (brain fog being a big one). There is data to suggest that even a small amount of food early will help with this, in part due to hormone regulation, and off the back of my advice she has now started eating early.
Food for thought.