Intermittent fasting is praised by many as an effective way to lose weight. But in fish it also affects the quality of eggs and sperm.
In recent years it has intermittent fasting become a real hype. People consciously choose to alternate a period of fasting with a period of normal eating. And because you lose a lot of weight in a short time in this way, more and more people are succumbing to this lifestyle. A pressing question, however, is what the effect of intermittent fasting is on your fertility. And so researchers decided to study the issue in zebrafish.
For those who don’t know exactly what intermittent fasting means, it is basically a form of intermittent fasting. “It’s an eating pattern in which people limit their food consumption to certain hours of the day,” said researcher Alexei Maklakov. The best known scheme is the 16/8 scheme. You choose to only eat between noon and eight in the evening. In addition, the 5:2 diet is popular, where you eat normally five days a week and very little on two days. “intermittent fasting is a popular health and fitness trend,” says Maklakov. “People do it to lose weight and improve their health.”
Meanwhile, it is known that intermittent fasting has numerous health benefits. Not only does it help you lose weight quickly, a previous study even showed that it can benefit people with diabetes, heart disease, high blood pressure and even cancer. Despite that, some things are still unclear. Because what does it do to our fertility, for example? “We wanted to know more about how these kinds of diets affect fertility in a well-known model organism,” says Maklakov.
The researchers decided to study the zebrafish, an animal that has become an increasingly popular model organism in science. Zebrafish can provide just as much fundamental biological knowledge as the most commonly used laboratory animal, the mouse. Moreover, the genome of the zebrafish is well known and has great similarities with that of mice. This makes comparison with humans at a cellular and molecular level possible. Finally, zebrafish have all major organs involved in metabolism and hence are used to study various human metabolic disorders.
In the current study, scientists studied what happens when zebrafish fast intermittently. “In our study, the fish didn’t eat for two weeks,” said co-author Edward Ivimey-Cook. Scientias.nl out. “This is still possible in the case of fish, by the way intermittent fasting be considered as they did not eat for a temporary period and then returned to their normal eating patterns. Importantly, we did not starve the fish (indicating malnutrition). They were simply deprived of food for a period of time. We know that different animals respond differently to dietary restrictions. And a two-week fast is considered in fish intermittent fasting.”
Egg cells and sperm
The findings show that intermittent fasting, at least in zebrafish, does not leave fertility untouched. It appears that it affects the quality of both eggs and sperm. “Initially, fasting only led to a reduction in the number of eggs, while the quality remained the same,” says Ivimey-Cook. “In this case, quality over quantity was maximized.” But after Lent, something remarkable happened. “As soon as the fish returned to their normal feeding schedule, more offspring were born again, but of lower quality. In this case, quality decreased as quantity increased.” The quality of the male sperm also decreased due to intermittent fasting. “The eggs fertilized by this sperm were less likely to survive,” says Ivimey-Cook.
In short, the scientists found that the quality of both eggs and sperm was negatively affected by intermittent fasting, even after the fish returned to their normal diet. And that indicates that intermittent fasting at least in zebrafish can cause fertility problems. “The way organisms respond to food shortages can affect egg and sperm quality,” Maklakov concludes. “And such effects could potentially persist beyond the end of the fast.”
Why is Zebrafish Fertility Declining? According to the researchers, this has to do with the body prioritizing its own health. “Everyone has a limited amount of energy that can be invested in something,” Ivimey-Cook explains when asked. “This energy can be invested in one’s own body condition or in reproduction. When available energy decreases, research in many species has shown that organisms invest in their own condition rather than in their reproduction.”
Now, of course, the question arises to what extent the findings also apply to humans. Zebrafish and humans are quite different. “We need more studies before we can determine the positive or negative effects of intermittent fasting in humans,” emphasizes Ivimey-Cook. “Only after further research can we say something meaningful about the effects in humans.”
However, according to the researcher, the findings underline “the importance of not only considering the effect of fasting on the body, but also its effect on the quality of eggs and sperm.” “We have shown that intermittent fasting and subsequent return to a normal diet can impact fertility,” summarizes Ivimey-Cook. “More research is now needed to understand how long it takes for sperm and egg quality to return to normal.”