New insights into how intermittent fasting affects women's reproductive hormones

New insights into how intermittent fasting affects women's reproductive hormones

Intermittent fasting has been shown to be an effective way to lose weight, but critics have feared the practice could have a negative impact on women's reproductive hormones. Now, a team of researchers at the University of Illinois Chicago has published a study on obesity that brings new evidence to the table.

The researchers, led by Krista Varady, UIC professor of nutrition, followed a group of obese pre- and postmenopausal women on the "warrior diet" method of intermittent fasting over a period of eight weeks.

The Warrior Diet prescribes a time-restricted eating window of four hours per day during which dieters can eat without counting calories before resuming a water fast until the next day.

They measured the differences in hormone levels, obtained by analyzing blood sample data, in groups of dieters who adhered to four- and six-hour feeding windows versus a control group that did not follow dietary restrictions.

Varady and her team found that levels of sex-binding globulin hormone, a protein that transports reproductive hormones throughout the body, were unchanged in the dieters after eight weeks. The same was true for both testosterone and androstenedione, a steroid hormone that the body uses to produce both testosterone and estrogen.

Dehydroepiandrosterone, or DHEA, a hormone that fertility clinics prescribe to improve ovarian function and egg quality, was significantly lower in both premenopausal and postmenopausal women at the end of the study, falling by about 14%.

While the decline in DHEA levels was the most significant finding of the study, DHEA levels remained within the normal range in both pre- and postmenopausal women through the end of the eight-week period.

This suggests that in premenopausal women, the small decrease in DHEA levels must be weighed against the proven fertility benefits of lower body mass. The drop in DHEA levels in women after menopause could be concerning because menopause already causes a dramatic drop in estrogen and DHEA is a major component of estrogen. However, a survey of participants found no negative side effects associated with low estrogen levels after menopause, such as sexual dysfunction or skin changes.”

Krista Varady, UIC professor of nutrition

As an added benefit, because high levels of DHEA have been linked to breast cancer risk, Varady said moderately lowering levels could be helpful in reducing this risk for both pre- and post-menopausal women.

The study measured levels of estradiol, estrone and progesterone; all hormones vital for pregnancy -; also, but only in postmenopausal women, due to the changing levels of these hormones during the menstrual cycle of premenopausal women. In postmenopausal women, there was no change in these hormones after eight weeks.

In both the four-hour and six-hour diet groups, women experienced weight loss of 3% to 4% of their baseline weight over the course of the study, compared to the control group, which had almost no weight loss. The dieters also saw a decrease in insulin resistance and oxidative stress biomarkers.

Perimenopausal women, typically around 40 years of age, were excluded from the study.

Still, Varady said, "I think this is a great first step. We've watched thousands of pre- and postmenopausal women through various alternate-day fasting and time-restricted eating strategies. All it does is make people eat less. By shortening that eating window, you're naturally reducing calories. Much of the negative information about intermittent fasting that's been reported comes from studies in mice or rats. We need more studies to determine the effects of intermittent fasting “To examine fasting on man.”

Source:

University of Illinois, Chicago

Reference:

Kalam, F., et al. (2022) Effect of time-restricted eating on sex hormone levels in premenopausal and postmenopausal women. Obesity. doi.org/10.1002/oby.23562.

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