Following time-restricted fasting — a type of intermittent fasting — diet plan may lead to fertility problems in both males and females, according to new research conducted on fish.

While intermittent fasting includes all intentional fasting patterns and doesn’t distinguish between fasting during the day or night, time-restricted eating calls for eating within a limited number of hours during daylight.

To understand the effects of time-restricted fasting, researchers at the University of East Anglia in the UK, studied zebrafish (Danio rerio).

The findings, published in the journal Proceedings of the Royal Society B, showed that time-restricted fasting affects reproduction differently in male and female zebrafish.

Once the fish returned to their normal feeding schedule, females increased the number of offspring they produced at the cost of egg quality resulting in reduced quality of offspring.

The quality of male sperm also decreased.

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The research team said that while the study was conducted in fish, their findings highlight the importance of considering not just the effect of fasting on weight and health, but also on fertility.

“Time-restricted fasting is an eating pattern where people limit their food consumption to certain hours of the day. It’s a popular health and fitness trend and people are doing it to lose weight and improve their health,” said Prof Alexei Maklakov, from UEA’s School of Biological Sciences.

“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,” Maklakov said.

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To find out what happens when individuals are exposed to food during and after a period of fasting, the team measured how males and females allocate resources to body maintenance versus the production and maintenance of sperm and eggs, and the quality of the resulting offspring.

“More research is needed to understand how long it takes for sperm and egg quality to return back to normal after the period of fasting,” said Dr. Edward Ivimey-Cook, from UEA’s School of Biological Sciences.