fasting for women. is it helpful or harmful?
a complete guide on if/how/when to fast for women…
Fasting has become one of the biggest wellness trends — from 16:8 to 5:2 — with promises of better energy, fat loss and longevity. But what works brilliantly for men doesn’t always suit women’s biology.
Years of study in nutrition, and to be honest with you, it still confuses me! There seem to be two schools of thought on this subject-
(Let’s name them)…The optimal protein pack…those that say you need to eat a gram of protein for every pound of ideal body weight. That skipping breakfast causes stress, breakfast is the most important meal of the day.
Then you have the fasting friends (rubbish name I know, but stay with me) who expound the effects of time restricted eating for autophagy (more on that later), weightloss and blood sugar regulation.
Actually, both of these perspectives have their merit. In this blog I will cover: the science, pros, cons, and how to know if fasting is right for you.
1. What Happens in the Body During Fasting
When we stop eating for a period of time, our body shifts from a fed (anabolic) state to a fasted (catabolic) one. In the fed state, insulin rises, nutrients are stored, and the body focuses on building and repair. During fasting, insulin levels fall and the body begins mobilising stored energy — first glycogen, then fat.
Two key cellular pathways are central to this process: mTOR and autophagy.
mTOR acts like a growth switch — stimulating protein synthesis, cell growth, and tissue repair. It’s activated when we eat, particularly in response to protein and insulin.
Autophagy is the body’s internal recycling programme. When nutrients are scarce, cells clean up damaged components and reuse them to maintain efficiency.
A healthy rhythm between these two systems — alternating periods of nourishment (mTOR activation) and rest/repair (autophagy) — appears to support longevity and metabolic resilience. The problem arises when the balance tips too far in either direction: constant eating keeps mTOR permanently switched on, but chronic fasting can suppress it excessively, impairing recovery and hormonal balance.
2. The Potential Benefits of Fasting
When used strategically, fasting can offer a range of benefits — especially when combined with nutrient-dense meals and a balanced lifestyle.
Metabolic Health
Short fasts (such as 12–14 hours overnight) can improve insulin sensitivity, lower fasting glucose, and support more stable energy levels throughout the day. This may help reduce cravings and promote fat metabolism.
Brain and Mood
Periods of fasting have been shown to increase BDNF (Brain-Derived Neurotrophic Factor), a compound that supports learning, focus, and neuroplasticity. Many women report enhanced mental clarity when fasting is done gently and not combined with sleep deprivation or excessive stress.
Cellular Renewal and Longevity
Autophagy helps clear damaged mitochondria and proteins — reducing oxidative stress and potentially slowing aspects of the ageing process. This is one reason fasting is often linked with longevity in animal studies and emerging human data.
Inflammation and Gut Rest
Digestive rest may reduce post-meal inflammation and support a healthier gut environment, particularly for those prone to bloating or sluggish digestion.
Key takeaway: Fasting can be a useful reset — but it works best when your body is already nourished, not depleted.
3. The Drawbacks and Risks — Especially for Women
While fasting can be beneficial, women’s hormonal systems are finely tuned to energy availability. Restricting food too aggressively or too often can backfire.
Hormone Disruption
The female body constantly gauges whether it’s a safe time for reproduction. Prolonged calorie restriction can lower GnRH, the hormone that signals the ovaries to produce oestrogen and progesterone. The result may be irregular periods, low libido, thyroid slowdown, and disrupted mood.
Blood Sugar and Stress
Fasting raises cortisol, our stress hormone. In women juggling busy lives, high cortisol plus low blood sugar can trigger anxiety, fatigue, irritability, and even mid-afternoon crashes.
Thyroid and Adrenals
Long fasting windows can suppress T3, the active thyroid hormone, leading to slower metabolism and colder hands and feet. If you’re already experiencing low energy, it’s best to focus on balancing blood sugar before experimenting with fasting.
Too Much Autophagy, Too Little Repair
Fasting constantly without sufficient re-feeding can down-regulate mTOR activity, reducing muscle maintenance and recovery. Over time this can worsen fatigue, particularly if protein intake is low.
Remember: Autophagy is the body’s clean-up crew, not a full-time job. You need fuel to rebuild after the clean-up.
4. Fasting and the Female Cycle
Women’s tolerance for fasting shifts across the month:
Follicular phase (day 1 to ovulation): Oestrogen gradually rises, metabolism is more stable, and the body often copes well with slightly longer fasts (e.g. 14 hours).
Luteal phase (after ovulation): Progesterone increases, appetite rises, and blood sugar becomes more sensitive — meaning your body may prefer regular, protein-rich meals.
Listening to these natural fluctuations — rather than following rigid fasting rules — helps maintain hormonal balance and prevent fatigue or cycle disruption.
If your periods are irregular, you’re perimenopausal, or under significant stress, prioritising nourishment and consistency will almost always yield better results than pushing fasting harder.
5. Smarter, Safer Ways to Fast (If You Choose To)
If you’d like to explore fasting, start gently and observe how your body responds.
✔ Begin with balance:
A simple 12:12 fast (e.g. 7 pm – 7 am) gives your digestive system rest overnight without stressing your hormones.
✔ Break your fast wisely:
Always end a fast with protein, healthy fats, and fibre — for example, eggs with avocado and greens, or Greek yoghurt with nuts and berries. This stabilises blood sugar and prevents post-fast crashes.
✔ Avoid fasting on high-stress days:
If you’ve slept poorly or feel anxious, eat breakfast. Cortisol and fasting don’t mix well.
✔ Hydrate and use electrolytes:
Thirst is often mistaken for hunger; adequate hydration supports energy and cognition.
✔ Watch for warning signs:
Persistent fatigue, hair loss, poor sleep, irritability, or missed periods are cues to stop fasting and focus on nourishment.
6. When Fasting Might Be Helpful
Gentle fasting can be valuable for certain situations, such as:
Early signs of insulin resistance or pre-diabetes.
Frequent snacking and unstable energy.
Occasional metabolic “resets” after periods of indulgence.
However, fasting is rarely a first-line approach for women dealing with burnout, hormone imbalance, or chronic stress. In those cases, rebuilding with steady meals, balanced macronutrients, and adequate calories is the foundation of recovery.
So-what’s the answer?
Fasting is a fascinating tool — one that can trigger powerful cellular renewal through autophagy, while balanced nutrition activates mTOR for growth and repair. Both are vital. The art lies in alternating between the two with awareness, not rigidity.
For many women, the best results come from gentle overnight fasting, steady blood-sugar balance, and nutrient-dense meals that leave you energised rather than depleted.
“Support before you stress.”
Once your body feels nourished and resilient, a little fasting can become a supportive rhythm — but never at the expense of your hormones or vitality.
If you’re wondering whether fasting could support or sabotage your energy, I can help you find the right approach for your body. Click on the link below to book a free discovery call. Where we can discuss how I will help you to discover your personalised path to steady energy, balanced hormones, and long-term vitality.
