The dietary approach of Intermittent fasting is a nutritional strategy that consists of alternating between periods of eating and fasting. This approach does not limit particular types of food, but instead emphasizes when to consume them.
According to a new study from the University of East Anglia, time-restricted fasting diets may lead to fertility issues. The study, published on April 12th, 2023, reveals that time-restricted fasting has differing impacts on reproduction in male and female zebrafish.
Examples of intermittent fasting techniques include the 16/8 method, which involves a 16-hour fasting period and an 8-hour eating window, and the 5:2 method, where individuals eat normally for five days and reduce their calorie intake to 500-600 calories on two non-consecutive days.
Importantly, the study found that some of the negative impacts on egg and sperm quality persist even after the fish resumed their normal eating habits.
The research team says 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.
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.
The research team studied zebrafish (Danio rerio) to find out what happens when individuals are exposed to food during and after a period of fasting. They 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.
Dr. Edward Ivimey-Cook, from UEA’s School of Biological Sciences, said: “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.
“Importantly, some of the negative effects on eggs and sperm quality can be seen after the animals returned to their normal levels of food consumption following time-restricted fasting.
“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.”
