Fasting for women

Fasting is gaining popularity and now many individuals have taken to documenting their experience online of intermittent or prolonged fasting.

Fasting is a very personal experience and whilst it’s a game changer for some people, it’s not unusual to have a negative experience with it.

It’s common for fasting to begin to feel like extreme dieting and trigger a disordered relationship with food.

If you’re stressed and busy it can also be too much for your body to handle.

It’s also important to consider the hormonal differences between men and women and how fasting can impact these variations.

Benefits of fasting

Research has shown that fasting can reduce certain risk factors for disease and weight gain especially by lowering insulin and blood sugar levels.

There’s also studies emerging to suggest it can also enhance your health by:

  • Improving digestive health and your gut microbiome

  • Rebalancing immune system and reducing chronic inflammation 

  • Improving cognitive function and mood health

Types of fasting

These can range from 3 days to over 30 days.

NOTE: all fasting should be undertaken with caution and prolonged fasts should only be done under medical or expert supervision.

A more common type of regular fasting is short, intermittent fasting (IF).

There are different ways you can intermittent fast, these include:

  • 16:8 fasting: involves eating for 8 hours (usually 12pm to 8pm) and fasting for 16 hours.

  • 5:2 approach: involves eating as usual for five days a week and limiting intake on the other two days to 500 to 600 calories.

  • Single-day fasting with longer fasts like 24 hours, usually one day per week.

  • The fasting-mimicking diet: involves having 3 to 5 low-calorie days a month instead of fasting weekly.

Fasting and weight loss

Weight loss is the most common reason people decide to experiment with IF.

Most types of intermittent fasting can result in weight loss.

In this review of 13 trials, 11 (84.6%) reported statistically significant weight loss.

It can also make the process of losing weight easier by:

  • Decreasing time needed for meal prep

  • Making your nutrition convenient when life gets busy

  • Removing any overthinking food options when travelling or away from home

  • Enabling you to make less decisions about food

  • Decreasing the opportunity to overeat

  • Helping you create a calorie deficit easily

During fasting, only water or zero-calorie drinks, like black coffee or tea, are permitted.

The negatives of fasting

A downside in the rising popularity of fasting for weight loss is that it’s also been transformed into yet another diet that sells books and products like ketone sticks, MCT oil and electrolytes to name a few.

But fasting is a very personal experience and what works for one individual can be a struggle for another.

It’s important to know:

  • Fasting is a stress on the body and mind. Whilst some degree of it may be beneficial it can potentially cause you to develop a negative relationship with food and impact your mood.

  • It’s important to reflect on your total stress load when you consider fasting. If you’re busy with work deadlines, training for a sports event or not sleeping properly the last thing you may need is an additional stressor.

  • For some people fasting can cause sleep disruption and symptoms like anxiety, shakiness and hot sweats likely due to low blood sugar levels.

  • The stress of fasting may cause a change in reproductive hormone levels

  • Fasting may increase constipation as meals trigger bowel movements. This can be an issue hormonally as reproductive hormones are cleared from the body via bowel movements.

Fasting and female hormones  

For some women, fasting isn’t far removed from age old dieting habits and could prompt binge eating, disordered eating patterns or an altered relationship with food.

The other thing to consider is that many fasting studies were performed on men and the female body has a different hormone profile that cycles across the month.

The hypothalamus and pituitary glands in the brain are constantly assessing the resources available and whether there is regular energy (calorie) intake that means the body has capacity for reproductive function.

The brain also observes feedback from the body in terms of adequate body fat, total stress load and nutrient status, it then communicates with the ovaries accordingly.

This is why extended, or excessive periods of fasting can disrupt menstrual cycles or cause them to stop altogether.

If you’re participating in regular exercise, underweight (or don’t carry much body fat) or are undergoing a period of stress it has an additive effect.

This is a reason fasting may be more appropriate with ageing and especially after menopause (when there’s no cycle) to mitigate the impact of insulin resistance that occurs and leads to weight gain.

Who shouldn’t fast?

Intermittent fasting is not suitable if:

  • If you have a history of eating disorders

  • You’re underweight due to illness or other reasons

  • You’re undergoing medical treatment (seek professional advice)

  • You’re trying to conceive, pregnant or breastfeeding

  • You’re highly active physically (seek professional advice from a registered nutritionist)

  • You have hypothalamic amenorrhea (no menstrual cycle)

Should you adapt fasting across your menstrual cycle?

Similar to the concept of changing your nutrition and exercise across your menstrual cycle, there are theories relating to fasting and the hormone changes that take place over the month.

In my experience women’s menstrual cycles are unique and I don’t believe there’s one size fits all here.

Here’s some helpful points to explore:

  • It’s best to listen your body, assess how you feel, trial some changes and see what works for you.

  • You may not wish to fast as your menstrual bleed approaches as blood sugar regulation alters and your cravings or appetite may increase.

  • For some women this also occurs around ovulation so this may be another time you change things up.

  • Instead of restricting intake, a good nutritional strategy is to increase your protein intake and eat some wholefood carbohydrates to stop any increased cravings leading to a chocolate blowout.

  • I often recommend supplementation with magnesium, B6 (as pyridoxal 5 phosphate), zinc and essential fatty acids (Evening Primrose oil and omega 3’s) to help with any menstrual symptoms.

  • The first part of the cycle (days 5-14) when estrogen is increasing is when most women report feeling able to fast. Insulin sensitivity tends to improve with estrogen rising and higher dopamine levels can increase your sense of motivation.

3 steps to healthy fasting

To obtain the best results from intermittent fasting it can be helpful to transition slowly and avoid shocking your body.

The following is a step-by-step guide to incorporating fasting int your routine:


  1. Start by ensuring you’re eating real, nutrient dense foods. Real food contains all the vitamins and minerals necessary for your body to develop the metabolic flexibility to multiple energy sources (including stored body fat) during a fast.

    Also, if you’re going to decrease the number of meals you eat, it goes without saying you need to eat nutritious ingredients to avoid any deficiencies.


  2. Next begin by implementing consistent mealtimes and not eating in-between meals.

    Reducing snacking and grazing and having a 3-to-5-hour gap between meals and a 12 to 13 hours overnight helps your body adapt to longer periods of not eating. Increasing protein at main meals is the key to going longer without food.


  3. Once you’ve established a regular meal routine, you will find your blood sugar levels are more balanced which means your energy and appetite are more stable.

    At this point, you can experiment with intermittent fasting if you wish to or simply skip the odd meal on a spontaneous basis because you’re not hungry.

    If you decide to experiment with any of the different models of intermittent fasting like 16:8 or 5:2, it may help to measure your progress by monitoring things beyond weight loss like your energy, mood, sleep and irritability.

Fasting not an option? Try TRE

You can obtain the benefits of fasting with minimal stress by simply shortening the window in which you eat every day.

This is known as ‘time-restricted eating’.

The practice of time-restricted eating limits your daytime eating window to 8 to 12 hours.

Studies show an earlier eating window may work better as this is when they are most physically and mentally active, for example 9am to 5pm rather than the common suggestion of 12pm to 8pm.

It also doesn’t need to be the shortest window for the greatest effect. Studies have confirmed extending your overnight fast to 12 to 13 hours can help lower your risk of cancer, diabetes and heart disease.

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