Intermittent Fasting: What It Really Means for Women’s Hormones, Energy and Metabolism
Intermittent fasting has transcended fad status to become a culturally significant dietary approach. In fact it's one of the most talked-about wellness trends today. It’s promoted everywhere - from podcasts to social media - with promises of weight loss, hormone balance, improved gut health, clearer skin and better energy.
Some people genuinely feel better when they change their eating window, but for others, fasting can have the opposite effect. The challenge is that most online advice about intermittent fasting doesn’t consider women’s biology, hormones, stress, menstrual cycles, or individual symptom patterns, all of which can significantly change how fasting feels. While some forms of intermittent fasting show metabolic benefits in controlled trials, the evidence is far more complex, and the potential harms significantly greater, than popularised messaging suggests.
This isn’t an article telling you fasting is “good” or “bad.” It’s a clear, balanced explanation of what intermittent fasting actually does in the body, where the hype comes from, and what to be mindful of if you’re considering it.
Intermittent fasting: the online claims
Intermittent fasting has been touted for:
weight loss without calorie counting
activating cellular repair and autophagy
balancing hormones
improving mental clarity
increasing energy
extending longevity
curing metabolic dysfunction
balancing hormones
But these ideas are often based on snippets of research, simplified explanations or a one-size-fits-all approach that doesn’t reflect how different bodies respond.
Intermittent fasting claims
The intermittent fasting narrative draws from research (predominantly short term studies in men, not women) about metabolic switching and autophagy. But it's been extrapolated far beyond the evidence to suggest that intermittent fasting is a panacea. Biohacking culture and male dominated fitness spaces have heavily promoted intermittent fasting, with very little acknowledgement of sex-specific hormonal risks. Most of the research has not been carried out on women across different cycle phases, perimenopause, stress levels or suffering with symptoms like fatigue, PMS or cravings.
Marketing often positions intermittent fasting as requiring no calorie counting or no dieting - appeals that resonate broadly. Influencer content on social media has polarised the narrative that when you eat matters far more than what you eat.
The research on intermittent fasting
Let's have a look at what the science says about intermittent fasting on some key areas:
Weight loss - in controlled trials, intermittent fasting does help support weight loss. But a number of studies have shown that much of the weight lost is lean muscle tissue rather than fat. This is a crucial distinction lost in popular messaging.
Metabolic improvements - intermittent fasting has been shown to support short term improvements in blood sugar levels, cholesterol levels and some inflammatory markers. But long-term effects are unclear with several studies finding that standard calorie restriction alone achieves similar results.
Cardiovasculr risk - a large study of 19,000 adults found that an 8-hour eating window was linked to a higher cardiovascular death risk. This contradicts the earlier thoughts that intermittent fasting is cardiovascular protective. The study highlights that the emphasis should be on what is eaten, rather than when. Overall this suggests that even if intermittent fasting creates metabolic improvements, these may not translate to better long-term health outcomes if dietary quality remains poor.
Women's hormones - in pre-menopausal women, intermittent fasting can impair ovulation and lead to menstruation irregularities.
Sex differences - a number of studies have shown that women often experience less weight loss than men on identical intermittent fasting protocols, and are more susceptible to intermittent fasting causing hormonal disruptions.
Muscle mass and bone density - multiple trials have documented that intermittent fasting leads to a reduction in lean body mass and bone density, particularly if there is insufficient protein intake and a lack of resistance training alongside. For women at risk of osteoporosis, or those with a history of undereating, this is a significant concern.
Who could intermittent fasting help?
Men with metabolic dysfunction (type 2 diabetes, high cholesterol, obesity) may see modest benefits from intermittent fasting, provided comprehensive dietary work is undertaken to ensure meals are full of whole foods, protein, fibre and nutrients). But even in this population standard calorie restriction achieves similar results with fewer hormonal risks.
Post-menopausal women with metabolic dysfunction may also benefit as they are less susceptible to the hormonal disruption that pre-menopausal women experience with intermittent fasting. It's important that the dietary foundations are in place in terms of nutrient quality and that resistance training is carried out alongside in order to prevent muscle and bone loss.
When to be cautious
Pre-menopausal women are one group who need to be cautious about intermittent fasting. Prolonged disruption to hormones (both sex horones and stress hormones) can have lasting affects on fertility and bone health. But caution is also needed in the elderly alongside those who are not prioritising protein intake (at least 30g with each meal) and resistance training because of the risk of substantial lean muscle tissue loss.
It's also important to consider what you are eating. Compressed eating windows can make it difficult to consume adequate calories and micronutrients, particularly for those with smaller appetites or higher nutrient needs. Specifically, deficiencies in iron, B12, zinc and magnesium have been well documented with intermittent fasting.
Diabetics may also wish to err on the side of caution. If you are on diabetes medication then you risk dangerous blood sugar drops with intermittent fasting, particularly if medication regimes are not adjusted.
Finally, intermittent fasting can trigger, or worsen, restrictive eating patterns in those with a history of disordered eating.
What to focus on instead
Whilst intermittent fasting may theoretically support metabolic flexibility and reduce insulin resistance, the benefits come with risks that often outweigh the gains in the population most likely to use this tool - young women.
Instead of relying on extreme fasting windows, many people feel better when they prioritise consistent, adequate calorie intake, nutrient dense foods and healthy fats for hormone synthesis. Eating in this way provides nutrients needed for appetite control, energy, hormones, digestion and metabolic health in a more sustainable, and enjoyable, way.
Want to find an alternative to fasting?
Intermittent fasting can be appealing when you’re struggling with symptoms or looking for structure. But it’s not automatically the best approach for every body.
If you’d like clarity on whether fasting might support or disrupt your hormones, digestion, energy or weight, I’d be happy to explore this with you in a personalised and supportive way. Book in a free call and let's chat.
Prefer to read at your own pace?
I share occasional, practical updates like this, and let people know when something new is published. You’re welcome to leave your email below