Does fasting affect periods? WUKA experts discuss intermittent fasting for women and how to safely fast during your menstrual cycle.
What Is Intermittent Fasting?
Intermittent fasting is also sometimes called ‘time restricted eating’. Put simply, it’s all about when you eat, rather than what you eat. We all fast- in that we consume no food or drink- each day as we sleep, and if you’re practising intermittent fasting you’re just extending that fasting period a little longer through the day.
The most common example of an intermittent fasting plan is the 16:8. This involves fasting for 16 hours, and then eating all your meals and snacks in a smaller, 8 hour window. You can, of course, fast for a longer period of time each day, or you can choose to have a longer window in which to eat. Intermittent fasting plans can be varied to suit you- some may fast for 20 hours each day, others may fast for the whole day, then eat as normal the next day. This is often referred to as 'alternate day fasting'. Ultimately, you fast, eat, repeat.
The purpose of intermittent fasting isn’t just to lose weight, although most people will naturally lower the amount of calories they consume because they’re eating during a shorter time period each day.
Studies like this 2017 one has also found that intermittent fasting can improve metabolic function, by reducing levels of insulin and glucose in the body- leading also to weight loss as a ‘side effect’. Other studies such as this one from 2021 has found that intermittent fasting can help to improve cognitive function and help to prevent the progression of brain-related disorders too.
There are increasingly more studies into the effects that intermittent fasting can have on our overall health. This review of such studies was done in 2020 and concluded that
“Intermittent fasting proved to be an excellent approach for a healthy body. Many IF studies confirm the therapeutic effectiveness on the human body. Various animal studies and human studies show the positive impact of IF on reducing obesity and overweight, visceral fat mass, skin disease, aging, blood pressure, stroke, boosting immune system, promoting autophagy, and many more.”
All of these benefits are thought to be due to changes that take place when we fast for longer periods of time each day. Our bodies switch from burning sugar stores to burning fat stores instead. As it does this, ketones are released into the bloodstream, which your body can use for energy.
But is intermittent fasting ok for everyone to do, and does it work the same for both men and women?
Intermittent Fasting May Affect Women Differently To Men
Although we’re seeing more studies into intermittent fasting, there is still a lot more research that needs to be done when it comes to the affect it can have on men vs women.
Some studies, such as this one conclude that there are no differences at all between men and women when it comes to time restricted eating; others such as this one found vast differences in the way our bodies respond.
This 2022 study looked a little further, into the effects of fasting on hormone levels in pre and post menopausal women. It found that during fasting, levels of dehydroepiandrosterone (DHEA) dropped, while levels of testosterone, androstenedione and sex-binding globulin hormone (SHBG) remained the same.
SHBG is a protein that is responsible for transporting reproductive hormones throughout the body. Testosterone and androstenedione are steroid hormones that both play a role in producing oestrogen.
DHEA is responsible for improving ovarian function and egg quality; the drop in these levels suggest that the weight loss caused by fasting could have a negative impact on fertility.
As previously mentioned though, more research is needed in this area- plus most studies out there tend to use men as their subjects. This means that there is a real lack of evidence based information for women when it comes to intermittent fasting, it’s benefits and it’s drawbacks.
Does Fasting Affect Periods?
Because intermittent fasting can lead to calorie restriction and weight loss, there is a chance that it could affect your menstrual cycle.
Losing too much weight too quickly can affect your period; restricting calories is seen as a stress to the body, and this can disrupt the balance of hormones, leading to problems with ovulation and a late or missed period.
Does Intermittent Fasting Affect Periods?
Fasting for long periods (36 hours or more) could potentially lead to irregular periods, but a shorter fasting window should be ok for most women.
If you practise intermittent fasting, it’s important to ensure that your eating window is long enough for you to consume enough calories to keep everything running smoothly. Around 16 hours fasting is usually just right for most women, and long enough for you to see the benefits of weight loss, if that’s your goal.
It’s important to be able to recognise if fasting is causing changes to your period, or if you can’t consume enough calories in your eating window. If this is the case, adjust the length of time that you fast- listen to your body, give it the fuel it needs and allow your menstrual cycle to settle back into its regular rhythm.
If your period does become heavier than usual, this is likely to be temporary, but keep tracking it to make sure and speak to your GP if you're concerned. And, of course, make sure you're protected- we recommend WUKA Ultimate period pants collection to keep you covered during your heaviest days, and always have a pair of spare period pants in your bag just in case you get caught unaware too
It’s worth noting that some women may benefit more from intermittent fasting than others. This study found that fasting during Ramadan led to reduced stress levels in women suffering with PCOS. This is backed up by this 2021 study, which also found that women with PCOS are likely to experience an improvement in symptoms. The study concluded:
“Eight-hour TRF [ Time Restricted Feeding] may have beneficial effects on improving menstruation, hyperandrogenemia and reducing weight especially body fat, decreasing insulin resistance and chronic inflammation in women with anovulatory PCOS. TRF may be suitable for PCOS women with appropriate counselling and patient management.”
If you’re not sure, speak to your doctor for advice on intermittent fasting and whether or not it’s suitable for you.
If you already practise intermittent fasting, it’s important to pay attention to the foods that you consume during your eating window. A healthy, balanced diet is much more beneficial to the body and mind and will ensure that your body is getting the nutrients it needs, despite it being in a shorter window. What you eat during your period is also important, so staying away from processed foods and excess sugar is a great idea too.
How many hours should a woman do intermittent fasting?
We’re all different and we all respond to fasting differently too. But because longer fasts could cause stress to the body, they can also have an affect on your period too. It’s a good idea to listen to you body and keep fasts around 16 hours at first.
If you’re able- and want- to fast for a little longer, you can give it a try once a week, working up to longer periods if you wish. If you do notice changes to your cycle, take that as a sign that your body needs a longer eating window.
Is intermittent fasting good for females?
Intermittent fasting can be a very effective tool for weight loss, not to mention the other benefits that can come along with it too. Women can benefit from fasting too, especially if overweight or suffering from metabolic disorders.
Some women with PCOS may benefit from the effects of fasting; weight loss and lowering levels of insulin and glucose can help to manage the symptoms effectively.
How much weight can you lose in a month with intermittent fasting?
As with any weight loss plan, intermittent fasting should be practised responsibly. Ultimately, it’s calorie restriction that leads to weight loss, so the rate at which you lose weight will depend almost entirely upon what you eat during your feeding window.
A safe and healthy rate of weight loss is around 1-2 lb per week. This is more likely to be sustainable for most, meaning that once you lose the weight you’re more likely to keep it off.
What are the best intermittent fasting hours?
For most people the 16:8 ration works best. This means fasting for 16 hours, for example while you sleep, and then eating in an 8 hour window., This could be eating breakfast at 10am, then finishing your last meal at 6pm that evening.
Some prefer to fast for longer periods with a shorter feeding window. Others might follow an alternate day fasting plan- eating a limited amount of calories one day, then following that with a normal amount the next, and repeating.
If you’re just starting out, a 10 hour eating window is sensible, then you can work your way up to fasting for longer periods. Start by pushing your breakfast back each day and make sure that you have enough time to eat a sufficient amount of calories to keep you going until you break your fast again the next day.
Is fasting good during periods?
Fasting is not a bad idea during your period necessarily, but there are hormonal changes taking place that might make it a little more difficult. Decreasing oestrogen levels can lead to PMS symptoms such as bloating, cramps and food cravings.
If this is the case, it might be kinder to your body to ease off on fasting for a few days. Listen to your body and don’t push it.You could always fast for a shorter window during your period, then go back to a longer window when you feel able.
Of course, some women may find that fasting during their period is fine, in which case congrats- keep going!
Can intermittent fasting affect your period?
Intermittent fasting, if done safely and sensibly, shouldn’t affect your period. But if you fast for longer than your body is comfortable with and/ or you lose too much weight too quickly, you may see changes to your period.
Disruptions to hormones caused by stress can lead to problems with ovulation, which can mean a late or missed period. If this is the case, reduce your fasting window and make a note of any changes that occur.
Can fasting cause heavy periods?
Irregular periods can be a negative side effect to fasting, and some women may find the their period is much heavier than usual. This could be a sign that your body is under too much stress, so reduce your fasting window and pay attention to the foods you’re eating too.