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Intermittent fasting is one of the biggest health trends to have emerged in the last few years, but is it right for perimenopausal women? Registered dietitian, Laura Clark, takes us through the science…

Fasting has long been advertised as a wonder for weight loss, with everyone from Jennifer Anniston to Halle Berry touting its health benefits. But what does the science say when it comes to intermittent fasting during perimenopause and the hormone rollercoaster? Here, Laura Clark, registered dietician, reveals all…

What is intermittent fasting?

“Quite simply, intermittent fasting means not eating – or eating low amounts of food – for short periods of time,” says Laura. There are different ways that people can choose to fast, including…

1. Time-restricted feeding – this is about carving out specific windows of time for eating and not eating. For example, the 16:8 protocol includes an 8-hour eating window and a 16-hour fast. So, you might choose to only eat between 12-8pm or 8am-4pm.

2. The 5:2 diet - this means eating just 500-600 calories per day for two days of the week and eating normally during the other five. 

3. Alternate day fasting - perhaps the most hardcore form of intermittent fasting, this involves not eating (or limiting food to 500 calories) for 24 hours every other day.

What happens in your body when you fast? 

“When we fast, our body doesn’t have its usual access to glucose – our body’s preferred fuel source – so it starts to break down fat into chemicals called ketones,” explains Laura. “These ketones are then transported to our cells and used as energy.”

When there’s an increased amount of ketones in our blood, we’re said to be in ‘ketosis – a state in the body where your body burns fat for energy instead of glucose. To reach a state of ketosis, you usually need to go without food for between 12–36 hours .

Does intermittent fasting during perimenopause work?

At a time when we feel like we’re fighting against our bodies, a way of eating that breaks down fat for us sounds like the magic bullet, but when we’re in a hormone transition, are the benefits the same as they would be for a woman in her 20s or 30s?

You still can’t argue with the fact that a high-quality ‘Mediterranean’ diet is best for your health

1. Can it help with perimenopausal weight loss?

The research is mixed, with many studies showing that intermittent fasting can help to accelerate weight loss, but only in the short-term. A recent review looked at 43 studies and compared intermittent fasting with ‘normal eating’ and calorie-restrictive diets. The review showed that intermittent fasting had more benefits than ‘normal eating’ where participants weren’t given any specific instructions around diet. 

Laura’s take for perimenopausal women:

“These studies were only across a couple of months, and the dropout rates were high, at around 40%,” says Laura. “This tells us that intermittent fasting is hard to sustain and stick to in the real world.” 

“The takeaway for me is that while fasting may not be the most sustainable way of eating, it may feel less like a traditional ‘diet’ if you’re looking to lose a little weight, especially if you don’t fancy counting calories. 

“When it comes to the best diet style for perimenopausal women, you still can’t argue with the fact that a high-quality ‘Mediterranean’ diet is best for your health, so it might be worth trying fasting in the short-term, then switching to a more sustainable, healthy way of eating, such as the Mediterranean diet,” says Laura.

2. Can intermittent fasting improve gut health?

Evidence suggests that some kinds of fasting may help to increase the diversity of your gut bacteria – and a healthy gut can help with all sorts of things, such as digestion, absorption of nutrients, brain and heart health and so much more.

A recent study found that men and women who fasted for 16 hours a day showed increased bacterial diversity – particularly an increase in anti-inflammatory bacteria and a decrease in pathogenic bacteria (bacteria capable of causing diseases). 

“These bacteria have been linked with a variety of health benefits, including better metabolic health , improved heart health , and a lower risk of obesity, cancer, and inflammatory bowel disease,” says Laura. 

Laura’s take for perimenopausal women:

“Perimenopausal women are prone to inflammation and the diversity of the gut microbiome is affected by our lack of oestrogen. Because of this, habits that support your gut are beneficial to women at this time. A 16-hour fast is pretty hardcore, so a 12-hour window might be more realistic and still comes with significant benefits. An alternative to support your gut biome is to eat lots of different types of fibre which you can achieve through aiming for lots of plant-based foods and diversity in your diet.”

3. Can it help protect us from disease?

Because of the effect that fasting can have on our weight, cholesterol and gut health, experts believe that it can help to ward off disease. However, research is also beginning to link fasting with a process called autophagy. 

“Autophagy means ‘self eating,’' says Laura, “and is essentially the process that your cells use to clean out and recycle old, damaged or abnormal proteins and cell components. It sounds a bit gory, but it’s actually a good thing, helping our cells to become more resilient and playing an  important role in maintaining healthy cells and preventing diseases like heart disease, diabetes, cancer and infection .” 

Fasting may actually make it harder to maintain muscle mass and physical activity levels

Laura’s take for perimenopausal women:

“Yes, fasting may be able to enhance autophagy, and it could be a simple and safe way to do this as we get older and our risk of disease increases. However, we can’t get too carried away with this. Most of our evidence currently comes from animal studies and the evidence in humans is limited."

Are there any downsides of intermittent fasting during perimenopause?

Because perimenopausal women are experiencing quite big hormone changes, fasting may help with some aspects of the perimenopausal journey, while being detrimental to others…

It may spike your stress levels

On the one hand, fasting might improve your body’s resilience to stress. But on the other, “remaining in a fasted state for extended periods will create a stress response in the body by raising levels of cortisol (our stress hormone),” says Laura. “Because the body is prone to inflammation and is less resilient to the effects of stress when we’re in perimenopause , restricting our food intake to the extent that it starts to impact our mood or stress levels could cause more damage than it achieves.”

It could result in muscle loss

During perimenopause, our lean muscle mass begins to decline, so working on building or maintaining muscle should be top priority if you’re in perimenopause. 

The problem with intermittent fasting, according to recent research , is that it could result in an equal loss of weight from both fat stores and lean muscle mass – and it’s important to really prioritise muscle maintenance during this stage of life.

In addition, fasting may actually make it harder to maintain muscle mass and physical activity levels as you may find that your energy levels dip on fasting days.

It’s hard to stick to

Eating very few calories on a regular basis with alternate days fasting or going without food for 12-16 hours is no easy feat. 

“You might experience low energy, low mood and cravings – three things that you could really do without around perimenopause,” says Laura. “In my experience, it also has the potential to create negative relationships with food and our body.”

Intermittent fasting during perimenopause tips

As with lots of things around women’s hormonal health, more research is needed to prove that intermittent fasting is better than other ways of eating when it comes to staying healthy during perimenopause. If you do want to give it a go, even for a few weeks, Laura has these tips:

Review your current eating habits

“Look at your eating habits and record what times you’re eating in a normal 24-hour period,” says Laura. This is the first step to eating in tune with what your body truly needs. It may help you identify whether you’re a late-night snacker, for example, or whether you need breakfast straight after waking up. Generally getting to know your current eating habits, allows you to work out if you can create a slightly longer fast. 

One way to do this might be by trying to eat earlier

“We know that we’re less capable of processing a meal as we age, so eating over a large time span and late into the evening, doesn’t give our bodies the opportunity to ‘spring clean’ everything inside.” So, as a first step, try moving your evening meal an hour earlier to start adjusting your habit.

Start with time-restricted feeding

“Think about what works with your daily routine and listening to body cues is really important. To begin with, see how your body responds to a 12-hour fast as a minimum. If this works for you, you could consider the 16:8 protocol.”

The bottom line

“The main thing to remember is that we don’t need to put ourselves through gruelling dietary regimes as punishment for gaining weight later in life,” says Laura. “We’re already going through a lot, so my advice would be to start small, listen to your body and experiment with healthy eating habits to find what works for you. 

Really, the only diet that has robust research for better health overall is the Mediterranean diet , which is much more easy to adopt. It’s also healthy for the whole family, so requires less of an overhaul mealtimes, which in turn means less valuable time for meal prep.