A Delicate Balance
Have you ever tried intermittent fasting, repeated longer fasts, or even fasting mimicking diets and experienced symptoms of sleeplessness, anxiety, fatigue, irregular periods, or infertility? The scientific research on laboratory animals backs you up! One rat study showed that only TWO WEEKS of intermittent fasting shrank ovaries, stopped menstrual cycles, and disrupted sleep.1 In another animal study when female rats were given an extremely low-calorie diet, they stopped their reproductive cycle and developed a significantly heightened response to stress.2 Why are women so sensitive to dietary changes? Reproduction.
Intermittent Fasting (IF) has risen in popularity as a health and weight management strategy. This food intake pattern, which cycles between periods of eating and fasting, is known for its potential benefits on body weight, metabolic health, and longevity. But its impact on hormone regulation, especially in women, deserves closer scrutiny as women tend to be more sensitive to dietary changes at the cellular level. Although the research is still sparse on women and fasting, we scoured the literature and found some revealing data.
Hormonal Changes: The Case of Androgens
One of the hormones significantly affected by IF in women is Dehydroepiandrosterone (DHEA). DHEA is a crucial hormone produced by the adrenal glands. It serves as a precursor to other hormones like testosterone and estrogen and plays a vital role in various bodily functions such as immune function, bone density, and mood regulation.3
Long-term IF can decrease DHEA levels, particularly in women. When the body is subjected to fasting, it triggers a number of physiological responses to conserve energy. One of these is the down-regulation of DHEA production, an energy-consuming process. This decrease can have different effects depending on the individual's health status and other lifestyle factors.4
Women's hormonal profiles are inherently different from men's and are often more sensitive to dietary changes. Women have evolved to be highly responsive to energy availability due to their potential for reproduction. As such, women's bodies can perceive prolonged fasting as a state of famine, triggering adaptive hormonal responses designed to conserve energy. This can lead to lowered levels of hormones like DHEA.5
Lower levels of DHEA may also be associated with several health concerns. For example, lower DHEA levels can lead to reduced production of downstream hormones, mainly testosterone and estrogen, impacting mood, energy levels, and overall hormonal balance. Additionally, since DHEA has an essential role in maintaining bone density, its long-term decrease could potentially increase the risk of osteoporosis, especially in postmenopausal women.6
A recent study suggests that intermittent fasting decreases androgen markers (Testosterone and the free androgen index) while increasing sex hormone binding globulin (SHBG) in premenopausal, obese women. The study also suggests that IF may reduce androgens in men, thereby causing androgen deficiency symptoms such as lower libido.7 Further research is needed in the human model to more thoroughly understand the mechanisms of action and long-term effects of IF on reproductive hormones and fertility.
Cortisol: The Stress Response
Cortisol, often known as the "stress hormone," plays a key role in our body's response to stress, including the physiological, hormetic stress induced by fasting. Intermittent fasting, especially when extended, may lead to an increase in cortisol levels. This increase is part of the body's natural response to fasting, perceived by the body as a form of physiological stress.8
Chronic elevations of cortisol can have undesirable effects, such as disrupted sleep patterns, mood swings, weight gain, and in some cases, more serious health issues like hypertension and type 2 diabetes. It's particularly important for women, who are more likely to experience stress and related symptoms, to monitor their cortisol levels while practicing IF.9
The window of time restricted eating also plays a role. One study found that dinner-skipping resulted in significantly reduced evening cortisol and non-significantly raised morning cortisol. Conversely, breakfast skipping resulted in significantly reduced morning cortisol. This blunting indicates a dysfunctional HPA axis, and may be associated with poor cardio-metabolic outcomes9. Again, additional human studies are needed to completely understand the complexity of fasting’s impact on cortisol, and clear delineation is needed for people to make an educated decision about whether fasting is right for them or not.
Your Health is Personal. Your Care Should Be, Too
Given the hormonal changes that can occur with long-term IF, adopting a balanced approach is key. This could involve shorter fasting periods, stress management techniques, or adjustments to the fasting schedule to align with the body's natural circadian rhythms. Given the current body of data, IF may even be beneficial in the short-term for women with PCOS, since the goal of therapy is to reduce the androgen load in that disease state.
References:
1.Kumar, S., Kaur, G, (2013). Intermittent Fasting Dietary Restriction Regimen Negatively Influences Reproduction in Young Rats: A stydy of Hypothalamo-Hypophysial-Gonadal Axis, PLOS ONE 8, no.1: e52416.
2.Bronwen, M. et al., (2007) Sex-Dependent Metabolic, Neuroendocrine, and Cognitive Repsponses to Dietary Energy Restriction and Excess. Endocrinology, 148(9): 4318-4333.
3.Genazzani, A. D., Lanzoni, C., & Genazzani, A. R. (2007). Might DHEA be considered a beneficial replacement therapy in the elderly?. Drugs & Aging, 24(3), 173-185.
4. Kalam F, Akasheh RT, Cienfuegos S, Ankireddy A, Gabel K, Ezpeleta M, Lin S, Tamatam CM, Reddy SP, Spring B, Khan SA, Varady KA. (2023)Effect of time-restricted eating on sex hormone levels in premenopausal and postmenopausal females. Obesity (Silver Spring).31 Suppl 1(Suppl 1):57-62.
5.Mattson, M. P., Longo, V. D., & Harvie, M. (2017). Impact of intermittent fasting on health and disease processes. Ageing research reviews, 39, 46-58.
6.Labrie, F., Luu-The, V., Labrie, C., Simard, J.(2020) DHEA and its transformation into androgens and estrogens in peripheral target tissues: Intracrinology. Frontiers in Neuroendocrinology, 22, 185-212.
7.Cienfuegos S, Corapi S, Gabel K, Ezpeleta M, Kalam F, Lin S, Pavlou V, Varady KA.(2022) Effect of Intermittent Fasting on Reproductive Hormone Levels in Females and Males: A Review of Human Trials. Nutrients, 3;14(11):2343.
8.Tsigos, C., & Chrousos, G. P. (2002). Hypothalamic–pituitary–adrenal axis, neuroendocrine factors, and stress. Journal of Psychosomatic Research, 53(4), 865-871.
9.Chawla S, Beretoulis S, Deere A, Radenkovic D. (2021)The Window Matters: A Systematic Review of Time Restricted Eating Strategies in Relation to Cortisol and Melatonin Secretion. Nutrients, 13(8):2525.
10.Staufenbiel, S. M., Penninx, B. W., Spijker, A. T., Elzinga, B. M., & van Rossum, E. F. (2013). Hair cortisol, stress exposure, and mental health in humans: a systematic review. Psychoneuroendocrinology, 38(8), 1220-1235.