October 16, 2025, 1:28 pm | Read time: 4 minutes
In a systematic review, researchers examined the effects of intermittent fasting combined with exercise on athletes’ performance and physical aging processes. The benefits of time-restricted eating are already well-known. But how do meal breaks–and thus regulated energy intake–affect people who need to summon strength and endurance on demand? Do the proven positive effects on aging also apply to them? FITBOOK explores the results of the study.
Intermittent fasting (also known as interval fasting) has evolved from a short-lived trend to an established and health-promoting dietary form. Research now even suggests that certain forms of intermittent fasting can significantly increase life expectancy.1 Of course, we don’t want to overlook that there are also studies that view intermittent fasting critically (FITBOOK reported).
It is fairly certain that meal breaks can support cell regeneration and thus slow down aging. But what about the corresponding effects on athletes or very active people? Specifically: Can the combination of intermittent fasting and intense exercise maintain–or even enhance–performance while promoting healthy aging? This was the subject of a recent review.2
Review on the Effect of Intermittent Fasting on Athletes
The subject of the investigation was previous studies that researchers sourced from the two major scientific databases MedLine and Cochrane. These were randomized controlled trials (RCTs) from the past five years that focused on intermittent fasting among physically active individuals. The 18 included studies varied greatly, such as in their duration and size, as well as the type of fasting examined. The eating windows ranged from four to twelve hours per day. However, the widespread 16:8 rhythm was the most common. The training programs discussed were also very diverse. Various participant groups were examined, from generally active individuals to recreational athletes to competitive athletes.
Details of the Analysis
The researchers considered a variety of parameters–from classic performance metrics (endurance, strength, and speed) to metabolic and cardiovascular markers like insulin, blood lipid levels and blood pressure. Some studies also provided information on biochemical and molecular markers related to aging and cell health. These include proteins like SIRT1 and LC3A, which indicate that repair processes are occurring in the cells. Additionally, the researchers were able to use data on epigenetic markers to estimate the biological age of the participants.
Athletic Performance Remained Stable or Improved
In their evaluation, the researchers found that fasting periods generally did not impair athletic performance. In some cases, they even improved it. This is surprising, as one might assume that time-restricted eating would compromise energy for sports, especially for more intense training sessions. However, negative effects on strength, endurance, or overall training performance were not confirmed in most studies.
Intermittent Fasting and Exercise Improve Metabolic and Inflammatory Markers
The observations suggest that the metabolism can adapt well to fasting. Researchers suspect that intermittent fasting allows the body to use stored energy more effectively. Hormonal adjustments, such as those involving adrenaline, cortisol, or growth hormones, can also support performance during fasting.
Several of the evaluated studies described positive effects on inflammatory processes. Participants who practiced intermittent fasting showed lower blood sugar and insulin levels, a more favorable blood lipid profile, and reduced inflammatory markers. Additionally, researchers found evidence in several studies suggesting that intermittent fasting and exercise activate cellular repair mechanisms, which are associated with healthier aging. These included increased levels of certain autophagy proteins.
The combination of intermittent fasting and high-intensity interval training (HIIT) proved particularly beneficial. Researchers emphasize that performance metrics and metabolic parameters improved most significantly in this context.
The Effect of Exercise on Inflammatory Processes and Metabolism in Aging
How the Combination of Intermittent Fasting and Training Affects Body Fat and Muscle Mass
Athletes Can Safely Fast–Good for Performance and Possibly Longevity
With their review, the researchers aim to provide a comprehensive overview of the current state of research on the interplay of intermittent fasting, exercise, and aging processes. The data lead them to conclude that time-restricted eating does not result in performance losses for active individuals. Instead, it seems to have health-promoting effects. However, whether these effects lead to a longevity effect, meaning a slowing of biological aging, remains open. The study authors emphasize that the current evidence is still limited and further research is needed to make reliable statements.
Limitations of the Study
They also point out various limitations. These primarily concern the heterogeneity of the evaluated studies, which makes comparison significantly more difficult. Furthermore, most of them are based on small samples and ran for only a short time, often just a few weeks. Thus, the observations do not allow conclusions about the long-term effects of intermittent fasting–neither on athletic performance nor on aging. According to the researchers, no formal assessment of bias risk was conducted in the review itself. This standardized process would be important to reliably assess the trustworthiness of the results.