Time-restricted fasting can cause fertility problems, study finds

[Apr. 13, 2023: JD Shavit, The Brighter Side of News]

University of East Anglia researchers have found that time-restricted fasting diets may lead to fertility problems, based on a new study conducted on zebrafish.

The study, published in the journal Proceedings of the Royal Society B, indicated that time-restricted fasting affects the reproduction of male and female zebrafish differently, with some negative effects on egg and sperm quality remaining even after the fish returned to normal feeding schedules. The researchers said the findings highlighted the importance of considering the impact of fasting not only on weight and health, but also on fertility.

The study’s co-author, Prof Alexei Maklakov, from UEA’s School of Biological Sciences, explained that time-restricted fasting is an eating pattern where people limit their food consumption to certain hours of the day, popularly used as a health and fitness trend for losing weight and improving health.

Maklakov added, “But the way organisms respond to food shortages can affect the quality of eggs and sperm, and such effects could potentially continue after the end of the fasting period. We wanted to find out more about how these sorts of diets can affect fertility in a popular model organism.”

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The research team found that time-restricted fasting affects reproduction differently in males and females, with females producing more offspring after returning to normal feeding schedules but at the cost of egg quality, resulting in lower quality offspring.

Meanwhile, the quality of male sperm decreased, highlighting the importance of considering the effect of fasting on both body maintenance and production of eggs and sperm. The researchers suggested that more research is needed to understand how long it takes for sperm and egg quality to return to normal after the period of fasting.

The study was carried out with funding from the European Research Council (ERC), the Biotechnology and Biological Sciences Research Council (BBSRC), and the Natural Environment Research Council (NERC), in collaboration with the Centre for Environmental, Fisheries and Aquaculture Science (Cefas).

The findings of the study have implications for the growing trend of time-restricted fasting diets, which have gained popularity in recent years as a way to improve overall health and longevity. The study suggests that while the benefits of time-restricted fasting may be numerous, individuals considering this diet should take into account the potential impact on fertility, particularly if they are planning to conceive.

Fertility experts have warned that the findings of the study could have wider implications for human fertility, as the reproductive system of zebrafish is similar to that of humans. Dr. Edward Ivimey-Cook, from UEA’s School of Biological Sciences, said, “This study provides important insights into the potential impacts of time-restricted fasting on fertility, and highlights the need for further research in this area. While the study was conducted on zebrafish, the reproductive system of these fish is similar to that of humans, and the findings could have wider implications for human fertility.”

The study is the latest in a growing body of research highlighting the potential risks of time-restricted fasting diets, which have become increasingly popular in recent years. While the diets have been shown to have numerous health benefits, including weight loss, improved blood sugar control, and reduced inflammation, some studies have suggested that they may also have negative effects on gut health and lead to an increased risk of developing eating disorders.

The potential impact of time-restricted fasting on fertility is a growing concern, particularly among women who are planning to conceive. Some experts have suggested that the diet may lead to hormonal imbalances that could affect ovulation and fertility, although more research is needed to understand the potential long-term effects.

The study’s findings also highlight the importance of considering the impact of fasting on overall health and well-being. While time-restricted fasting may offer benefits for weight loss and overall health, it is important for individuals to consider their individual needs and to consult with a healthcare provider before embarking on any major dietary changes.

According to the National Institute of Diabetes and Digestive and Kidney Diseases, time-restricted fasting can help individuals lose weight and reduce the risk of certain chronic diseases such as diabetes and heart disease. However, the effectiveness of the diet may depend on factors such as the type of food consumed during the feeding period and the duration of the fasting period.

Dr. Ivimey-Cook added, "We are not saying that time-restricted fasting is bad. It may have health benefits, and we are not suggesting that people stop doing it. However, our study shows that it is important to consider the impact of fasting on reproduction and to consult with a healthcare provider before starting any new dietary regimen."

The study's findings may have implications for human fertility, as previous research has shown that fasting and other dietary changes can affect reproduction in mammals. However, more research is needed to determine whether time-restricted fasting has similar effects in humans.

In the meantime, the research team plans to investigate the underlying mechanisms by which time-restricted fasting affects reproduction in zebrafish. They also hope to determine how long it takes for sperm and egg quality to return to normal after a period of fasting.

The research was funded by the European Research Council (ERC), the Biotechnology and Biological Sciences Research Council (BBSRC), and the Natural Environment Research Council (NERC).

Note: Materials provided above by The Brighter Side of News. Content may be edited for style and length.

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