An increasingly well-liked weight-control strategy is time-restricted eating. This entails eating all of your meals and snacks during that time and fasting outside of it.
Evidence suggests that it may also reduce the risk of metabolic illnesses like diabetes. Some people find that it aids them in losing weight or maintaining a healthy weight.
An unfavorable effect of time-restricted eating on zebrafish fertility was discovered in a recent study. More study is required to find out similar occurrences in humans.
A type of intermittent fasting called time-restricted eating (TRE) emphasizes meal timing rather than calorie intake. It entails sticking to a rigid schedule of eating all of your meals and snacks — often between six and twelve hours each day. And only consuming water and calorie-free beverages outside of that window.
When following a TRE plan, a participant will select the eating window that best fits their lifestyle. By limiting their eating window, many people discover that they tend to eat less. This may make it an easy way to manage their weight. In recent years, the practice has grown in acceptance.
According to studies, TRE has various advantages. People with obesity who followed a 10-hour eating 14-hour fasting schedule for 8 weeks experienced clinically significant weight loss. Also, improvements in fasting blood glucose levels were observed. When obese women followed an 8:16 fasting schedule for three months, similar weight loss was observed.
Results haven’t always been favorable, either. According to a meta-analysis of 43 trials, calorie restriction was the best weight loss strategy, while intermittent fasting had a smaller impact.
TRE was found to have deleterious impacts on the quality of sperm and eggs in zebrafish. These effects persisted even when normal feeding was resumed.
Little impact on physical growth
For the study, the researchers employed zebrafish (Danio rerio), a little tropical fish that shares more than 70% of its genome with people. Zebrafish are tiny, thrive in big shoals in tanks, and reproduce quickly, making them a popular choice for research.
All of the fish had been fed an unrestricted diet before the experiment and were sexually mature. They were then randomly split into two groups by the researchers. One kept up the unrestricted diet, while the other went on a fast. The entire fish was added back to the diet after 15 days, according to the researchers.
The researchers measured the tail fin to determine somatic (body) growth during the 15-day experimental phase and after the animals were allowed to resume unrestricted feeding. They also evaluated reproductive performance, including the quality of the eggs and sperm produced.
The study’s authors discovered no distinction in somatic growth between the fish that had been fed normally and those that had been starved. Female fish, however, exhibited quicker fin growth than male fish after the fasting fish were put back on their regular diet.
Decline in egg and sperm quality
Females that were fasting had fewer offspring overall than those who were eating normally during the fast. However, the distinctions between fed and fasting fish vanished once they started re-feeding.
The quality of the offspring did differ before and after fasting, according to the researchers. Females produced fewer, but higher-quality children when fasting. The number of progeny increased once the fasting females resumed feeding, but their survival rate decreased.
Similarly, there was a decline in the quality of male sperm both during the fast and when feeding resumed.
Thus, fasting appeared to have a deleterious impact on gamete quality in both sexes, and the effects persisted even when normal food was resumed. According to the researchers, when food was scarce, fish focused more of their energy on maintaining their bodies and surviving rather than reproducing.
Similar effect on people?
UEA’s School of Biological Sciences professor and study’s corresponding author, Alexei Maklakov, stated: “Time-restricted fasting is a well-liked fitness and health trend that people follow to get in shape and lose weight,”
Prof. Alexei Maklakov stated, “But the way organisms adapt to food scarcity can affect the quality of eggs and sperm, and such effects could possibly persist after the end of the fasting period.”
Few research on the effects of TRE on fertility and reproduction have been conducted thus far, and the majority of these have involved rodents. The few human investigations, the majority of which had modest sample sizes, created more questions than they did answers.
Studies on humans
An extremely limited window (4-6 hours) for eating was discovered in a recent study to result in lower DHEA levels in obese women. DHEA is a steroid hormone that is crucial for the production of both estrogen and testosterone. Although this study was modest, experts emphasized the necessity for comparative studies in adults who are of a healthy weight.
Although the authors highlighted that there was little data in this area, another evaluation of papers revealed that intermittent fasting may lower androgen indicators in both men and women. This effect might help women with the polycystic ovarian syndrome (PCOS), but it could also have negative effects on men, like a loss of muscular mass.
The University of Illinois at Chicago’s Dr. Krista Varady, a professor of nutrition who was not involved in the study, has written extensively about TRE, She uttered:
Overall, I don’t believe that humans can benefit from these zebrafish research findings. According to findings from TRE studies conducted on humans, fasting has almost no negative effects on either a woman’s or a man’s reproductive hormones.
More study is required
Even though this study was done on fish, the authors claim that the results demonstrate how crucial it is to take into account how fasting may affect human fertility.
The study’s corresponding author, Dr. Edward Ivimey-Cook of the School of Biological Sciences at the University of East Anglia, said:
These findings emphasise how crucial it is to take into account not just how fasting affects body maintenance but also how it affects egg and sperm production.
He continued, “More research is needed to determine how long it takes for sperm and egg quality to get back to normal following the fasting period“.
Every year, hundreds of TRE articles in humans are published. I believe that rather than worrying about what is occurring in other non-mammalian species, we should concentrate on human discoveries. Humans and fish have radically different reproductive processes, making them quite different creatures. If this study had been conducted on people, it would have had a considerably greater impact.
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