Intermittent fasting is a diet that focuses on when you eat over what you eat. Although there are several different ways to intermittently fast, all methods are based on choosing a time frame to eat and a time frame to fast. For example, some people may eat within a strict eight-hour period during the day and forgo eating outside the scheduled time, whereas others might eat one meal a day, two days out of the week.
According to Johns Hopkins Medicine, this is an effective way to lose weight because going hours without food forces the body to exhaust its sugar stores and instead start burning fat – this is known as metabolic switching.
“Intermittent fasting contrasts with the normal eating pattern for most Americans, who eat throughout their waking hours,” Johns Hopkins neuroscientist Mark Mattson explains. “If someone is eating three meals a day, plus snacks, and they’re not exercising, then every time they eat, they’re running on those calories and not burning their fat stores.”
It’s recommended to eat healthy during the allotted eating times, avoiding junk food, greasy food, and other treats. Although no food should be eaten while fasting, water and other zero-calorie beverages, like black coffee and tea, can be consumed.
In addition to weight loss, studies also show that intermittent fasting improves memory, blood pressure and overall heart health, physical performance, potentially reverses a diabetic person’s need for insulin therapy, and reduces tissue damage.
The Negative Side Effects of Intermittent Fasting
Despite its potential benefits, intermittent fasting is not a one-size-fits-all solution. And although studies are limited, some say it may not be suitable for women at all.
The International Sports Sciences Association (ISSA) published a blog post last year highlighting the different ways male and female bodies react to periods of fasting. According to research, during short periods of fasting, “men’s metabolisms increase up to 14%.” Intermittent fasting also helps increase testosterone utilization and growth hormone by up to 200%, improves blood lipids to increase hormonal production, and decreases the risk for cardiovascular disease.
In an effort to conserve energy and store fat, women’s metabolisms slow down to cope with a long-term fast.
Women, in contrast, respond much differently. Research shows that in an effort to conserve energy and store fat, women’s metabolisms slow down to cope with a long-term fast. Additionally, women may also find a 50% increase in the stress hormone cortisol and a decrease in insulin sensitivity, meaning that intermittent fasting could cause women to gain weight, putting them at a higher risk of diabetes.
Harvard Health also notes several other side effects of intermittent fasting, including headaches, lethargy, crankiness, constipation, overeating, and extreme weight loss. Reportedly, it may also cause stomach irritation if you use medication that should be taken with food.
How Does Intermittent Fasting Affect Fertility?
Daily Mail reports that one in every ten adults in the United States intermittently fasts. In addition to several risks associated with this popular weight loss method, new news has come to light about the negative impact fasting may have on a woman’s hormones.
Typically, the production of two hormones is disrupted – luteinizing hormone and follicle-stimulating hormone, which prepare the body for ovulation by regulating your cycle. Because intermittent fasting requires the body to go extended periods without food or nutrients, it can cause hormonal deficiencies. As a result, your period may become irregular or stop entirely.
Although it’s rare for intermittent fasting to cause infertility, if you aren’t getting your period, you aren’t ovulating, which erases your chances of getting pregnant. Speaking to Daily Mail, Carolyn Williams, a dietician, explained, “It's kind of a cascade of effects on hormones from there.”
A food and wellness TikTok influencer who goes by the handle @Spark.It.Up posted a video a couple of years ago relaying her experience with intermittent fasting and how it impacted her periods. “I did intermittent fasting,” she says, “and I used to do it strictly. I thought there was no harm because I saw these benefits on YouTube.”
“It’s so good to let your body digest food and give it a little break and stuff,” she continued, “but bruh, I guess for women, it’s not good for your hormones, and I definitely experienced that.”
Dinara Mukh, a health and mindset coach boasting nearly 100,000 followers on TikTok, also posted a video sharing her thoughts on why intermittent fasting is not beneficial to women. “Intermittent fasting is not good for a female with an active menstrual cycle,” she says. “Intermittent fasting should go through a period of feasting and fasting. However, most of the studies have been done on men and have adverse effects on the female body.”
“When you don’t eat for a long period of time, your blood sugar plummets,” she says, “and then when you eat again, your blood sugar spikes. So, if you have issues with the blood sugar, anything that causes blood sugar to go up and down will be harmful to your hormones.”
“Your blood sugar is more sensitive in the second half of your cycle, so doing anything that messes with your blood sugar in the second half of the cycle will cause a lot of hormone imbalances,” she says, adding that, “the most optimal fasting for women is to fast for 12 hours between dinner and breakfast. Otherwise, don’t do it.”
While intermittent fasting has risen in popularity over the last decade, garnering over 1.5 billion views on TikTok, its efficacy is still widely debated. Last year, the Journal of Clinical Endocrinology & Metabolism published a study following 36 people with diabetes who intermittently fasted for three months. The study concluded that 90% of participants were able to decrease their dosage of diabetes medication.
In 2017, another study found that a person could achieve significant weight loss and improved glucose levels after two weeks of intermittent fasting.
In contrast, another study published in June found intermittent fasting is no better than basic calorie counting when it comes to losing weight, Daily Mail reports.
Of course, there are so many external factors that can impact a woman’s menstrual cycle. But because there is minimal evidence on how intermittent fasting affects women, it's important to weigh the risks before diving into any weight loss regimen, regardless of its popularity on TikTok.
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