To Be Great, you must feel great. For many women, that involves maintaining a healthy weight.
Intermittent fasting is a popular method of eating to lose weight for men and women. It involves alternating periods of eating and fasting and has many health benefits, including weight loss, cholesterol reduction, and decreased blood pressure.
But what effect does intermittent fasting have on women’s hormones?
This article will explore how different styles of intermittent fasting affect hormones and how it can benefit women’s health. We will also discuss the potential risks associated with intermittent fasting and how it may affect women differently than men.
Note: In this article, we will explore how intermittent fasting impacts different hormones associated with the female sex. This may differ from an individual’s gender expression. For this article, we use the terms “female” or “woman” to refer to the biological sex (i.e., the sex assigned at birth). Those who are intersex or undergoing hormone therapy should consult their medical provider for more information on how intermittent fasting may affect them.
Types of Intermittent Fasting
Our guide to intermittent fasting can give you more information on how to implement different types of fasting. The type of intermittent fasting you follow affects your hormone levels. Here’s a quick overview of the most well-studied IF methods.
- 5:2 Diet is when you follow your regular diet for five days and significantly restrict calorie intake on two nonconsecutive days (usually ~500 calories per day).
- Time Restricted Eating (TRE) is where you consume your daily calories in a set window of time and fast for the remainder of the day (e.g., 8 hours eating, 16 hours fasting).
- Meal Timing involves dividing the day’s calories unequally throughout the day, eating more in the morning, afternoon, or evening.
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Different Female Hormones and How Fasting Affects Them
Hormones play a vital role in the overall health of women. Beyond their role in reproduction, female hormones regulate many bodily functions, including metabolism and mood.
Out of balance hormones can lead to various health issues, such as fatigue, weight gain, depression, and infertility. Hormones that are extremely out of balance for a prolonged period of time can cause other severe health complications like polycystic ovarian syndrome or increased risk of breast cancer.
Hormone regulation is integral to overall health, so you need to know how your diet or fasting can affect them. This is especially true if you already suffer from hormonal issues. There are five main types of female hormones, and they all are produced in different parts of the body and control and affect different systems. Here is a rundown of what they are, what they control, and how intermittent fasting impacts them.
While there are human studies around female hormones and intermittent fasting, it’s far from a well-studied topic. There are some gaps in the research, especially for specific subsets of age and weight.
Estradiol is one of the most impactful forms of estrogen, a hormone that plays a vital role in developing and maintaining female reproductive organs. It is produced mainly in the ovaries but also by the adrenal glands and fat cells. Estradiol helps regulate menstrual cycles, fertility, bone health, and other bodily functions. It also helps to maintain healthy skin and hair.
However, excess estrogen also can lead to polycystic ovarian syndrome, anovulation (when an egg doesn’t release during the menstrual cycle), and an increased risk of breast cancer.
There has only been one trial done on intermittent fasting and estradiol levels. It was explicitly around meal timing and studied women with PCOS with elevated estradiol levels. If they ate more than 50% of their calories at dinner instead of eating more than 50% at breakfast, their estrogen levels rose by a clinically significant amount.
While this hasn’t been studied in women without PCOS, this finding suggests eating more food early in the day, for women with elevated estradiol levels, may be better. Of course, research in women without PCOS is needed to confirm this thought.
Androgens are a type of hormone responsible for developing and maintaining male characteristics. But in addition to their role in male development, androgens also have essential functions in women’s health, such as regulating menstrual cycles and controlling fertility.
High levels of testosterone in women is known as hyperandrogenism and can cause excessive hair growth, scaly patches on the body, and problems with the menstrual cycle.
In one study, premenopausal women with obesity followed the 5:2 intermittent fasting style in which they consumed 500 kcal two days per week. In six months, their free androgen index (FAI) levels had decreased, meaning they had a lower abnormal androgen status.
Another study followed women with PCOS and obesity who ate all their calories before 4 pm and only drank water afterward. Within five days, they’d lost 2% body weight and had lower levels of androgen than those who ate more calories at dinner.
To support these findings, a study that compared the women who ate the majority of their calories either at breakfast or dinner showed that the group that ate earlier in the day had lower androgen markers. Interestingly, these levels decreased without any weight loss.
The three studies indicate that eating calories earlier in the day may help lower androgen levels in premenopausal women or those with PCOS.
SHBG (Sex Hormone Binding Globulin) is a protein the liver produces that binds to sex hormones, such as testosterone and estrogen. It helps regulate the amount of these hormones in the bloodstream, ensuring they are available when needed. SHBG also plays a vital role in fertility and reproductive health, as it helps ensure enough of these hormones are available for proper functioning.
The concentration of SHBG increased with weight loss with 8-hour TRE intermittent fasting for women with PCOS and the 5:2 diet for premenopausal women with obesity. In addition, those who followed meal timing with the consumption of calories earlier in the day had higher levels of SHBG even without weight loss.
Gonadotropins are hormones that impact the reproductive system, produced by the pituitary gland. They regulate the production of sex hormones, such as testosterone and estrogen. Gonadotropins also help to control the development of reproductive organs, like the ovaries and testes.
Only one study has been done on the connection between these hormones and intermittent fasting. In this study, it was found that the level of gonadotropins did not increase or decrease after following 8-hour TRE for five weeks, though the participants did lose weight.
Prolactin is a hormone produced by the pituitary gland in the brain. It regulates many bodily functions, including:
- Growth and development
- Reproductive processes.
It is also involved in the regulation of mood and stress levels. High prolactin levels can lead to infertility, irregular menstrual cycles, and other health issues, so it’s important for women to maintain normal levels as much as possible.
Weight loss doesn’t have much effect on prolactin levels, and the one study done on prolactin levels and intermittent fasting showed no change after almost six months of following the 5:2 diet. This is a good sign for lactating women who want to try intermittent fasting, since prolactin is the primary hormone involved.
Intermittent Fasting and Hormones: A Positive Relationship
While the research still has a lot of gaps, there is evidence that forms of intermittent fasting may have positive effects on specific female hormone imbalances.
Some of these positive changes may be related to the effects of weight loss as a result of intermittent fasting. But some hormonal benefits have been observed even without weight loss, which is good news for those who want to balance their hormones without losing weight.
According to the research to date, the best form of intermittent fasting for hormone balancing across the board comes from eating a higher percentage of daily calories in the morning and curtailing food intake in the evening. However, intermittent fasting works best when you choose a plan that works best for your lifestyle.