It has also been shown to improve weight loss and athletic performance. While none of the health benefits have been duplicated in humans to date, the athletic benefits have been seen, though to a lesser degree and not in the ways one might expect.

In human trials, intermittent fasting may be a viable strategy for weight loss, but only for those who are very much overweight. Adults who are closer to their ideal weight do not seem to benefit.

For active adults who are close to their ideal weight, intermittent fasting may even have negative effects. One study showed that those who fasted did not add as much muscle mass as those who normally ate when both groups followed a structured strengthening program.

With respect to performance in endurance sports, intermittent fasting does have an impact but possibly not in the way that athletes might hope. Many studies have shown that athletes actually perform significantly worse when they train during a fasting period.

This is not terribly surprising as the absence of readily available carbohydrates is sure to have an impact on performance. When comparing performance in two groups of people after being fed, where one group has normally been eating, and the other was intermittently fasting, both groups performed comparably.

However, the group that was fasting intermittently was making use of fats as their primary metabolic fuel, while the group that ate normally used carbohydrates.

This is very interesting, but given the absence of real performance benefits, one could wonder if it really matters.

One thing about intermittent fasting, across all of the human trials that I reviewed for this article, was certain; it is not easy. All of the studies on intermittent fasting report very high dropout rates.

When asked why subjects would routinely say that the fasting protocol was simply too difficult to adhere to. In the end, intermittent fasting remains theoretically very interesting.

It has shown very compelling health benefits in lab animals but continues to be difficult for humans and of uncertain benefit. Still, given the potential upsides and the relative paucity of negative findings, this may be a nutritional strategy that some wish to pursue. For those who wish to give this a try, you need to consider the following:.

Do you have a question about this or anything else related to health, wellness and triathlon? Fasting for weight loss: An effective strategy or latest dieting trend, Johnstone A, International Journal of Obesity, vol: 39 5 pp: Hydration Collection.

Race Day Collection. Recovery Collection. Fasting diets have become increasingly popular over the last several years, with the promise of weight loss and performance benefits. They have especially gained traction among dieters and bodybuilders looking to lose weight, with an increasing number of endurance athletes practicing it to increase fat oxidation capacity in their muscles.

However, there are varying schools of thoughts and opinions on the matter: while some may swear by fasting, others call it a waste of time and energy. If you ever thought about how this diet could possibly help or harm your performance, keep reading to learn more!

Fasting is defined as the abstinence from consuming food and beverages for different periods of time. This is when you consume all of your calories within an 8-hour feeding window and fast the other 16 hours. Other types of fasting include the , where you eat normally for 5 days and restrict energy intake for 2 days to calories, and when you consume nothing for days at a time.

However, those practicing intermittent fasting usually tend to be in a caloric deficit due to lesser frequency of meals. What does fasting do on a physiological basis? Several hours after eating, our insulin levels decrease which allows our fat cells to release their energy stores to use as fuel.

When we fast for hours or more, our liver glycogen stores are depleted so we rely on our adipose tissue for energy. The central idea of fasting is to allow our insulin levels to go down far and long enough that we burn fat instead of glucose.

There have been animal studies done that indicate promising benefits of fasting in the general population. Fasting has been shown to lead to weight loss and better blood pressure, cholesterol levels, and blood sugars.

Hence, fasting has been shown to reduce the risks of obesity and other metabolic disorders due to its effects on metabolism and hormones such as insulin.

Furthermore, studies show that fasting is safe in humans and can be effective if done correctly. So for weight loss, fasting can definitely be useful for those who have trouble overeating to regulate their calories throughout the day by having a more regimented eating schedule. But what about for endurance athletes?

Can fasting provide any benefits in performance? Let us walk you through some pros and cons! Perhaps the biggest argument for fasting is that it increases an athlete's fat oxidation capacity, supposedly leading to more efficient fat burning, prolonged energy, and an overall improved performance.

Because our glycogen stores are limited, fasted training forces the body to utilize fat as energy. Overtime, your body learns to adapt to burning fat rather than glycogen, providing sustainable energy during longer workouts since adipose tissue provides many more calories of energy than glycogen does.

Essentially, fasting can help your body become better at metabolizing fat rather than relying on carbohydrates. Although the pros sound promising, further investigation is needed to analyze the effects of fasting on endurance athletic performance. There is conflicting data regarding the effects of fasting on glucose metabolism and physical performance in trained athletes.

While some studies report decreased performance while fasted, others find no significant effects at all. Even though fasting may allow for an increased ability of the muscles to use fat as fuel during exercise, it is unclear if this effect translates to better performance.

There is evidence showing that relying on fat as fuel actually fails to enhance performance in long endurance races and athletes may find it difficult to continue performance at high intensities. Furthermore, subjects usually show increased levels of perceived fatigue even if performance was not compromised.

Another concern is that fasting oftentimes results in decreased caloric intake, which affects numerous aspects of health and performance. As of now, there is little evidence to support the idea of endurance training and fasting-mediated increases in fat oxidation.

It is generally recommended that endurance athletes should avoid high intensity training while fasting. For all athletes, it is crucial to consume a sufficient amount of energy and nutrients to support performance. Inadequate energy intake can result in fatigue, weakness, and overall decreased performance.

Because endurance athletes have greater nutrition requirements than the average population, fasting may be an impractical approach. There are still studies that need to be done to improve our understanding of the effects of fasting in endurance athletes. So feel free to experiment with different types of diet, see if it agrees with your body, and remember that the best diet is the one that you can stick to!

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Thus, the question becomes can IF achieve the same benefits as calorie restriction? To answer this question, it is first important to understand what IF actually is. There are many different approaches to IF, the most popular being the method.

This style of IF entails abstaining from all food intake for hours per day. For the remaining 8-hours adherents can eat normally with no need to count calories or avoid certain foods. One of the major draws to IF is the fact that you do not have to restrict what or how much you eat, but simply when you eat.

It can take a while to adjust to ignoring a growling stomach at specific hours. However, for those who can stick with it and adapt, the benefits may be worth it. When it comes to weight loss the results are clear; IF works.

Studies have shown that individuals following an IF diet lost just as much weight as those on a calorie-restricted diet and reported lower hunger levels over time. Studies indicate that IF is not a magic bullet for weight loss. That weight loss is relatively short-lived — almost all long-term studies observed that after a year IF participants regain the weight that they lost.

Although disappointing, this is not altogether unexpected. The reason relying on fatty acids and ketone bodies elicits so many potential health benefits is still a bit of a question mark; researchers have yet to definitively determine why our bodies seem to fare better health-wise when fueled from fat.

Regardless of the how, many are also left wondering whether athletes can reap these benefits on an IF diet without seeing their performance suffer.

Before IF became so trendy, some athletes were already trying to navigate periods of fasting with training and competition. For centuries, many religions have included traditions and rituals that incorporate various forms of fasting.

Of particular interest is the Muslim tradition of Ramadan. For the month-long period of Ramadan, Muslims abstain from all food and beverages from sunup to sundown.

Although not a precisely a hour fast, it comes pretty close and because of that, Muslim athletes have served as an ideal study population when considering how fasting can impact athletic performance.

The bad news is these studies may leave us with more questions than answers. However, a subsequent study on elite judo athletes found little effect of fasting on aerobic performance or speed.

Conflicting outcomes such as these are largely representative of the lack of consensus when it comes to the performance impact of fasting during Ramadan. In addition, very few studies have been carried out in women.

Also, the lack of a control group in most studies means the effect of intermittent fasting cannot be isolated.

So for the moment, it is not possible to draw a conclusion about the effectiveness of intermittent fasting on athletic performance. Athletes who wish to use intermittent fasting should consider several practical issues before starting.

Are their training schedules compatible with this dietary approach? For example, does the period during which an athlete is allowed to eat allow them to consume enough food prior to doing physical exercise or to be able to recover after the training?

And, importantly, what about food quality, given that athletes must consume sufficient protein to recover and maintain their lean body mass and limit negative impacts on their performance? Intermittent fasting may result in an energy deficiency that is too great for athletes with high energy needs to overcome.

This could be the case for endurance athletes running, cycling, cross-country skiing, triathlon, etc. due to their high volume of training. These athletes may end up suffering from Relative energy deficiency in sport RED-S , a syndrome that affects hormone secretion, immunity, sleep and protein synthesis, among other things.

If the deficit is prolonged, this will have an adverse effect on an athlete's performance. It is also important to question the motivation for adopting a dietary practice as strict as intermittent fasting.

Some people do it for religious reasons such as Ramadan. Others are motivated by weight control goals and the hope of achieving an "ideal" body according to socio-cultural norms. A recent study showed a significant association between intermittent fasting in the past 12 months and eating disorder behaviors overeating, compulsive exercise, vomiting and laxative use.

Although this study does not determine whether fasting causes eating disorders or eating disorders lead to fasting, it does highlight an associated risk in this practice. Finally, the potential impact of intermittent fasting on social interactions must also be considered.

A fasting schedule may limit participation in social activities that involve food. What is the risk of negatively influencing the eating behaviors of other family members, especially children or teenagers who see their parents abstain from eating and skip meals? During prolonged endurance events, sugars often get consumed and depleted, necessitating the less efficient metabolizing of these secondary fuels.

So, if there was a way to make those processes more efficient, an athlete would have an advantage. Intermittent fasting has been posited as a means of doing just that.

By regularly stressing the body and depriving it of readily available carbohydrates, we force our cells to utilize fats and, to a lesser extent, protein and maximize cellular efficiency. But does the theory translate into reality?

A lot of research has been done on intermittent fasting, and while the results have not been uniform, they are still very much worth consideration. Before discussing some of the results, it is important to first note that intermittent fasting can mean many different things. Different researchers have used wildly differing protocols e.

For example, in lab animals, intermittent fasting has been shown to increase lifespan and decrease all manner of chronic diseases. It has also been shown to improve weight loss and athletic performance.

While none of the health benefits have been duplicated in humans to date, the athletic benefits have been seen, though to a lesser degree and not in the ways one might expect. In human trials, intermittent fasting may be a viable strategy for weight loss, but only for those who are very much overweight.

Adults who are closer to their ideal weight do not seem to benefit. For active adults who are close to their ideal weight, intermittent fasting may even have negative effects.