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At the end of the holiday (and feasting) season tends to spark a renewed desire to “spring clean” our bodies. It’s a prerequisite during Christmas time to devour rich and delicious food without a care for its calorie profile. However, your body may be in a sluggish state if you feel you committed this “carbicide” crime in excess. Consequently, your weight gain woes may compel you to jump on the popular fasting bandwagon.

Fasting of all kinds is doing its trendy rounds in the wellness industry. It has been praised for its health benefits – namely weight loss, lowered inflammation, and improved blood sugar levels. Naturally, it may be tempting to do a fast immediately to clear out the vacation “gunk”. Perhaps it appeals to the revival of your “new year, new me” journey. But doing it too soon – and in the wrong way – has its setbacks, especially for women.

A history lesson on fasting

Fasting is when you abstain from eating food. Generally, traditional diets are rooted in what to eat, while fasting is based on when to eat. This eating style begins the moment you swallow your last bite of food. But it ends instantly after you polish off your first spoon – or a forkful of your next meal. Essentially, the idea is to allocate a time window to healthy eating and one to calorie restriction. Thereafter, you rotate between the two. Fasting lowers the body’s insulin levels and gets it to burn stored fat for energy.

This way of eating dates to a time before the agricultural revolution. Our hunter-gatherer ancestors participated in this act regularly, albeit inadvertently. They would oscillate between periods of food excess and food scarcity. There was no such thing as indulging in breakfast upon waking or heating leftovers to wolf down. As foragers, they would remain in their fasted state until they had an opportunity to catch or find food.

Eating three meals a day: how we went from fasting to feasting

Trekking for days on end to find food became a thing of the past with the advent of farming. It meant greater food security and being able to eat more than ever. Currently, the most common eating pattern in society is three meals a day – plus snacks. The ability to store our food and social routines that became associated with mealtimes most likely gave rise to this structure. Although, no scientific evidence supports “three meals a day” as the “normal” approach to food intake.

Going food-free for a period was standard if we consider the conditions from which we have evolved. This was largely dependent on the environment and season in which earlier communities found themselves.

Today, food is accessible at every corner, along with diet-related diseases (such as obesity and diabetes). Our predecessors – on the other hand – would remain healthy, despite giving their digestive systems unplanned time off. Therefore, scientists believe that fasting may prevent and help treat these issues because it imitates the food availability of ancient times. Only, it is vital to understand how fasting impacts different people.

A woman cannot fast like a man

Biologically speaking, women have a different metabolic response to fasting than men. The reason for this is hormones. Certain stages of a woman’s cycle benefit from fasting, while others take a nose-dive. It affects ovulation and menstruation in a big way and may put your cravings out of whack if not done thoughtfully.

According to a 2018 study, a rise in progesterone (during the premenstrual phase) creates cravings for sugar, salt, and fat. In other words, fasting at this time is a recipe for disaster; you will be more prone to the wrath of unhappy hormones (and an insatiable appetite). For example, a 2022 study found that people who followed a low-carb diet or would fast intermittently had higher levels of binge eating and food cravings when compared to non-dieters.

Certainly, fasting as a lifestyle regimen is mostly safe for improving women’s health. However, there are optimal times in which to fast. Also, it may be beneficial to consider the guidance of a physician if you are unsure. It needs to be done at the right time and in the right manner best suited to a woman’s cycle. Hence, women need to be attuned to which hormones are at play (and at which times) to avoid the physical stress that can come with fasting.

Allow your menstrual cycle to call the (fasting) shots

Women who are in their child-bearing years should plan their fasts according to their menstrual cycle. Using an app like Flo can make it easier for you to track which phase you are in to avoid wreaking havoc on your hormones. There is no perfect fasting method but aligning it with your body’s circadian rhythm and cycle is recommended.

Dr. Mindy Pelz is an expert in women’s health and a pioneer in tailoring fasts to support our menstrual cycles. Here’s a rough outline of how to fast (assuming you have a 28–35-day cycle) that is loosely based on/inspired by Dr. Pelz’s suggestions:

  • Menstruation Phase (days 1-7, roughly):

    Estrogen production begins the day your bleeding starts. Circadian fasts are best during this phase. It involves aligning your meals with your body’s internal clock and not eating in the time between sunset and sunrise. It may seem counterintuitive, but it’s okay to fast during your period. Just be sure to prioritize nutrient-dense foods. It is suggested to stock up on spinach and other leafy greens to replenish your iron. On top of that, consuming magnesium-rich foods (like dark chocolate and pumpkin seeds) can ease any nasty cramps.

  • Follicular Phase (days 8-14, roughly):

    This phase begins right after your period comes to an end. Your estrogen is still rising (along with your energy) which makes it an ideal time to push for longer fasts than normal. Additionally, your body’s ability to clear blood glucose is at its best. For this reason, you can increase your carbohydrate intake to sustain yourself during exercise.

  • Ovulatory Phase (days 11-14 is the ovulation window, more or less):

    Estrogen and testosterone peak while your ovary releases a mature egg to await fertilization. At this stage, you should not do intermittent fasts that exceed 15 hours. You can support estrogen by eating meals high in probiotics, prebiotics, and polyphenols.

  • Luteal Phase (days 15-28):

    The early stage of this phase (days 15-21) is when you should start opting for high-protein, low-carb foods. Your progesterone levels are also on the rise, a hormone that does not take kindly to stress of any kind. In the second stage (days 22-28), progesterone starts to decline and cravings for calorie-dense foods may occur. Therefore, you should not participate in long fasting periods and heavy exercise. Honor your cravings for carbs by swapping unhealthy versions for starchy vegetables like sweet potatoes and carrots. This is a time to nurture your body and refrain from calorie restriction. That being said, if pregnancy is not your goal, you can fast for no more than 13 hours if you would still like to.

Are there other times when a woman should not fast?

Studies have shown that women with body fat percentages below 20% are at risk of developing hormone irregularities. Fasting may contribute to this risk, so it may be best for these women to steer clear of the practice altogether.

Additionally, irregular periods can occur in some women who fast due to their insufficient calorie intake. This is because cortisol increases when you go too long without food. Too much of this stress hormone during the second half of your cycle (the luteal phase) can suppress progesterone.

Ovulation is dependent on progesterone as it prepares the uterus lining for a fertilized egg to grow. Moreover, the absence of pregnancy signals the uterus lining to shed in the form of monthly menstruation. So, in simple terms, no ovulation means no period. Therefore, a woman must be clear on her energy needs and body composition to determine how to approach a fast.

Moreover, fasting is not recommended if you are:

  • Pregnant or breastfeeding.
  • Try to become pregnant (unless you are obese or overweight).
  • Struggling with an active eating disorder.
  • Experiencing menstrual dysfunction unrelated to being overweight or obese.

The bottom line

Fasting can be a fantastic addition to your health regimen. But it should not be used to hastily course-correct a bad day (or a few) of eating. A restricted eating window can have a negative effect on female sex hormones (estrogen and progesterone) if done without proper care.

It’s better to prepare your body for a fast by eating whole foods for a few days first instead. After that, pay heed to which phase of your cycle you are in. If you work with your hormones, and not against them, you will reap a wonderful boost to your health.

References

Alvero, R.; Kimzey, L.; et al. (1998, January). Effects of fasting on neuroendocrine function and follicle development in lean women. National Library of Medicine. https://pubmed.ncbi.nlm.nih.gov/9435419/.
Colombarolli, M.S.; De Oliveira, J.; et al. (2022, December). Craving for carbs: food craving and disordered eating in low-carb dieters and its association with intermittent fasting. National Library of Medicine. https://pubmed.ncbi.nlm.nih.gov/35999438/.
De Souza, L.B.; Martins, K.A.; et al. (2018, November). Do Food Intake and Food Cravings Change during the Menstrual Cycle of Young Women?. National Library of Medicine. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10316899/.
Kim, B.H.; Joo, Y.; et al. (2021, August 27). Effects of Intermittent Fasting on the Circulating Levels and Circadian Rhythms of Hormones. National Library of Medicine. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8419605/#:~:text=For%20humans%2C%20cortisol%20begins%20to,levels%20%5B80–82%5D.
Mattson, M.P.; Allison, D.B.; et al. (2014, November 25). Meal frequency and timing in health and disease. National Library of Medicine. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4250148/.
Michalsen, A.; Li, C. (2013, December 16). Fasting therapy for treating and preventing disease – current state of evidence. National Library of Medicine. https://pubmed.ncbi.nlm.nih.gov/24434759/.
Nair, P.M.K.; Khawale, P.G. (2016, April-June). Role of therapeutic fasting in women’s health: An overview. National Library of Medicine. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4960941/.
Caela Bennett

Caela Bennett

Caela Bennett is a wellness content writer and holistic health coach. She hopes to enlighten people through powerful storytelling and offer clarity when navigating the noise within the realm of health. In addition, she guides others in awakening their self-discovery journey and embodying the best version of themselves. Her work is rooted in the philosophy of alchemy: turning metal into gold, i.e., transforming one thing into something better. While she is a maximalist in expressing herself through words, she is a minimalist in lifestyle pursuits.

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