Intermittent Fasting Affects Egg, Sperm Quality, Harms Fertility: Study

Time-restricted or intermittent fasting, an eating pattern whereby people limit their food consumption to certain hours of the day, could cause fertility problems, according to a new research.

The research team, led by University of East Anglia (UEA), UK, also said that it was important that they observed some of the negative effects on eggs' and sperms' quality after the fish returned to their normal levels of food consumption.

They further said that despite being conducted in fish, the study highlighted the importance of considering not just the effect of fasting on weight and health, but also on fertility.

The study is published in the journal Proceedings of the Royal Society B.

"Time-restricted fasting is a popular health and fitness trend and people are doing it to lose weight and improve their health.

"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," said Alexei Maklakov, professor from UEA's School of Biological Sciences.

To find out what happened when individuals were exposed to food during and after a period of fasting, the researchers measured how males and females zebrafish (Danio rerio) allocate resources to body maintenance versus production and maintenance of sperm and eggs.

They also studied the quality of the resulting offspring.

"What we found is that time-restricted fasting affects reproduction differently in males and females. 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.

"These findings underscore the importance of considering not just the effect of fasting on body maintenance but also on the production of eggs and sperm," said Edward Ivimey-Cook, from UEA's School of Biological Sciences.

He also said that more research was needed to understand how long it took for sperm and egg quality to return back to normal after the period of fasting.