Is Intermittent Fasting/Time Restricted Eating or Alternate day fasting, healthy for women? : A Naturopathic Perspective
In recent years, various fasting protocols have gained popularity for their so called ‘potential health benefits’, including Intermittent Fasting aka time-restricted eating (TRE), fasting, and alternate-day fasting (ADF). While these practices can offer promising results, it is crucial to consider if the research for fasting has been performed on women. Fasting affects women’s hormones and metabolic health profoundly differently males.
My experience with fasting began early in my 20s when I completed a long water fast as part of a journey to heal the many symptoms of Chronic fatigue I had. I chose to do this supervised at True North in California. My fast was completed successfully. However what I noticed was that most of the physicians there were men and there was no discussion on the impacts of fasting on females physiology compared to males. No one told me it might take a while for my period to return, or that my PMS may improve from fasting. Also should I continue to eat within a certain window or is this not healthy long term? I had so many questions and no sound science to answer them. Its been a decade since this time and since then there has been more research conducted for women. In this blog post, we will explore the strength of the scientific evidence surrounding these fasting patterns and discuss their potential advantages and disadvantages for women.
Intermittent Fasting
Intermittent Fasting or Time-Restricted Eating (TRE): Time-restricted eating involves consuming all meals and snacks within a specific time window each day while abstaining from food during the remaining hours. To be clear TRE is not actually calorie restriction although often because you are eating in a window usually between 12-8 hours you do naturally eat slightly less. Here are some pros and cons to consider:
Pros:
Improved metabolic health: Several studies have shown that TRE can positively influence weight management, insulin sensitivity, and lipid profile, potentially reducing the risk of metabolic disorders in women. (1)
Simplicity and flexibility: TRE is relatively easy to implement, as it primarily involves adjusting meal timings rather than restricting specific food groups.
Enhanced sleep quality: Restricting food intake closer to bedtime might improve sleep quality and help regulate circadian rhythms (2). We have known for a long time that there is a circadian clock that is regulated by light. This is through the suprachiasmatic nucleus (SCN) in the hypothalamus. There are also peripheral clocks that are regulated by food intake. Eating at times that are opposing the natural rhythm of the peripheral organs leads to deleterious changes in glucose metabolism and lipid metabolism(2).
TRE may be beneficial to anovulatory Polycystic Ovary Syndrome. A study was conducted where women with PCOS were placed on an 8 hour TRE program. There were improvements to weight loss, specifically reductions in body fat, it improved menstruation regularity, improvement in hormones relating to hyperandrogenemia, improved insulin resistance and chronic inflammation.(3)
Cons:
Most of the research has been performed on obese individuals, animals and on men. There is not enough research to say that every women and specifically women without chronic disease/health concern would benefit from TRE.
Adherence challenges: For some individuals, adhering to a restricted eating window can be difficult, especially if they have irregular schedules or social commitments that conflict with the desired time frame.
Nutritional and caloric adequacy: Restricting the eating window may lead to a reduced opportunity to consume a balanced diet, potentially affecting the intake of essential nutrients. If calories are also reduced this could lead to a caloric deficit which can affect fertility. These include Relative Energy Deficit (REM), mainly occurring in highly active women, and Hypothalamic Amenorrhea. Both disrupt menstrual cycles and ovulation making them irregular or even stop (4).
While some women with diagnosed health conditions may benefit from TRE, others might not experience the same advantages or may even face adverse effects such as changes to their menstrual cycle. I recommend asking yourself what your goals are? Personal factors such as age, hormonal status, and overall health should be considered. If your looking to eat in a time based way to optimise digestion Time Based Eating (TBE) may be better for you. More about this below.
Alternate Day Fasting
Alternate-Day Fasting (ADF): ADF involves alternating between days of unrestricted eating and days of caloric restriction or complete fasting. There has been one study on women to date that compared continuous caloric restriction to restricted calories on just two days per week. Here are the pros and cons to consider:
Pros:
Weight loss potential: ADF has shown promising results for weight management for young overweight women, as the calorie restriction on fasting days can create a significant caloric deficit over time (5). Calories were restricted on only 2 days per week for 6 months and it was as effective as continuous calorie restriction(CER) for weight loss. (5)
Insulin sensitivity improvement: ADF may enhance insulin sensitivity and glucose metabolism, more than continuous calorie restriction. (5)
ADF has shown to enhance cardiovascular health. It may reduce inflammation, improve lipid biomarkers, and improve blood pressure(5). Specifically reducing Total LDL cholesterol and triglycerides.
Cons:
Restriction of calories on 2 days per week may create a false pretense that an individual can eat whatever they like on other days of the week. Eating less two days a week is not going to make up for eating poorly 5 days a week over the long term and may create disordered eating habits.
ADF may affect regularity of menstrual cycles. In one study ADF across 6 months increased the average length of the menstrual cycle.(5)
Surprisingly, ADF was shown to be as hard to implement into a lifestyle as continuous caloric restriction. (5)
How does fasting impact Women’s Hormones?
The hormone response to fasting is different between men and women (Study). Below are some ways it may be beneficial or where it may be harmful.
Menstrual cycle: As mentioned previously in the article, fasting has shown to lengthen the menstrual cycle and also cause irregularity. Caloric restriction involved in any type of fasting can impair ovulation and cause Hypothalamic amenorrhea (Complete loss of the period).
PCOS: Research suggests that intermittent fasting may improve insulin sensitivity, potentially leading to better blood sugar control and weight management in women. This has shown to be beneficial in conditions such as PCOS, Obesity and other metabolic disorders.
Thyroid Hormones: The thyroid gland produces hormones that regulate metabolism, regulate other hormones such as progesterone and estrogen and much more. How does fasting influence thyroid hormones in women?
Studies suggest that intermittent fasting may decrease T3, our active thyroid hormone. Women were placed on a calorie restricted diet for 12 months which led to significant decrease in T3. Lower levels of T3 long term may lead to alterations in metabolic rate. (6) In another study women were put on a 14 day water only fast. T4 and T3 decreased but there was also an enhanced synthesis of reverse T3 (rT3) and a enhanced break down of rT3. (7) These results demonstrate that for someone struggling with a thyroid concern fasting should be monitored and may not be right for you. However, the studies failed to mention how many of these women’s thyroid hormones returned to normal post the fast.
More research is needed to understand the long-term implications of these changes. I typically would not recommend TRE or extreme TBE to people with Hypothyroidism, or for women who are trying to become pregnant as normal levels of T3 is important to be able to conceive.
What kind of fasting is right for me?
The various types of fasting can have complex effects on women's hormones and weight. While some studies show it may improve insulin sensitivity, stimulate growth hormone release, and contribute to weight loss and muscle preservation in women, it is essential to consider individual variability and potential effects on the menstrual cycle. I believe fasting is a tool and can be used appropriately short term to support wellness. However it is not something we should be doing year after year 24/7. As women our hormones change over our lifetime and thus what is a health contributing practice also is different depending on our age and stage.
What about Time Based Eating?
If you are healthy and free from disease, I like Time Based Eating (TBE). We remove triggering words like ‘restriction’ and we focus more on eating in alignment without digestive cycles (circadian rhythm). We have known for a while that we have a wake clock that is regulated by light. Well our digestive systems are regulated by different clocks that receive messages when we eat. TBE encourages us to notice when our digestive system may need to rest and prioritizes eating during the times of day when we are more able to break down and absorb our food. This leads to not only improved metabolic health but also reduces indigestion, inflammation and bloating for many women. TBE involves eating within a window of 14 hours to 8 hours. It is recommended to make your largest meals Breakfast and Lunch when your digestive system is at its strongest. It also is recommended to not eat to close to bed time. This gives your digestive system 1.5-2 hours rest prior to sleeping. As the old saying goes, eat breakfast like a Queen, lunch like a Princess and dinner like a Pauperess.
If you are suffering from a PCOS, cardiovascular concerns, obesity, or other inflammatory lifestyle diseases then another fasting protocol may be helpful to help you reach your heath goals.
If considering intermittent fasting or alternate day fasting it is advisable to consult with a healthcare professional who can provide personalized guidance based on individual health needs and goals.
If you are after support to know if fasting is right for you and how to do it effectively and safely please book a consultation or a clarity call.
References
1 Harvie, M. N., Pegington, M., Mattson, M. P., Frystyk, J., Dillon, B., Evans, G., Cuzick, J., Jebb, S. A., Martin, B., Cutler, R. G., Son, T. G., Maudsley, S., Carlson, O. D., Egan, J. M., Flyvbjerg, A., & Howell, A. (2011). The effects of intermittent or continuous energy restriction on weight loss and metabolic disease risk markers: a randomized trial in young overweight women. International journal of obesity (2005), 35(5), 714–727. https://doi.org/10.1038/ijo.2010.171.
2. Moon, S., Kang, J., Kim, S. H., Chung, H. S., Kim, Y. J., Yu, J. M., Cho, S. T., Oh, C. M., & Kim, T. (2020). Beneficial Effects of Time-Restricted Eating on Metabolic Diseases: A Systemic Review and Meta-Analysis. Nutrients, 12(5), 1267. https://doi.org/10.3390/nu12051267.
3. Li, C., Xing, C., Zhang, J., Zhao, H., Shi, W., & He, B. (2021). Eight-hour time-restricted feeding improves endocrine and metabolic profiles in women with anovulatory polycystic ovary syndrome. Journal of translational medicine, 19(1), 148. https://doi.org/10.1186/s12967-021-02817-2
4. Pedreira, C. C., Maya, J., & Misra, M. (2022). Functional hypothalamic amenorrhea: Impact on bone and neuropsychiatric outcomes. Frontiers in endocrinology, 13, 953180. https://doi.org/10.3389/fendo.2022.953180.
5. Harvie, M. N., Pegington, M., Mattson, M. P., Frystyk, J., Dillon, B., Evans, G., Cuzick, J., Jebb, S. A., Martin, B., Cutler, R. G., Son, T. G., Maudsley, S., Carlson, O. D., Egan, J. M., Flyvbjerg, A., & Howell, A. (2011). The effects of intermittent or continuous energy restriction on weight loss and metabolic disease risk markers: a randomized trial in young overweight women. International journal of obesity (2005), 35(5), 714–727. https://doi.org/10.1038/ijo.2010.171.
6. Weiss, E. P., Villareal, D. T., Racette, S. B., Steger-May, K., Premachandra, B. N., Klein, S., & Fontana, L. (2008). Caloric restriction but not exercise-induced reductions in fat mass decrease plasma triiodothyronine concentrations: a randomized controlled trial. Rejuvenation research, 11(3), 605–609. https://doi.org/10.1089/rej.2007.0622.
7. Límanová, Z., Sonka, J., Kratochvíl, O., Wilczek, H., & Marek, J. (1981). Effects of total fasting in obese women. IV. Response of serum triiodothyronine (T3) and reverse triiodothyronine (rT3) to administered T3. Endokrinologie, 77(1), 70–78.