Intermittent fasting diets could cause fertility problems, according to new research.

The scientists behind the study looked at male and female Zebrafish - Danio rerio - to find out what happens when they are exposed to food during and after a period of fasting.

The team measured how Zebrafish allocated resources to body maintenance, body production, maintenance of sperm and eggs, and the quality of offspring.

And they found that some of the negative effects on eggs and sperm quality were seen after the fish returned to their normal levels of food consumption.

Female Zebrafish saw an increase in the number of offspring they produced but saw a drop in egg and offspring quality, and the male's sperm also decreased in quality.

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

However, more research is needed to understand how long it takes for the quality of the sperm and egg to return back to normal after the fasting period.

What is Intermittent fasting?

Intermittent fasting is a type of diet in which people do not eat for an extended period of time.

There are different forms of intermittent fasting, which include:

• 5:2 diets - Consuming only 500 - 600 calories for two days each week

• 16:8 plan - This involved eating during an eight-hour window and fasting for 16 hours

• Alternative day fasting - Fasting every other day

• 24-hour fasts

'A popular health and fitness trend'

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

"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."

This study was led by the University of East Anglia in collaboration with researchers at the Centre for Environmental, Fisheries and Aquaculture Science (Cefas).

It 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).