Intermittent fasting and sport: a false good idea?
Intermittent fasting is gaining more and more popularity and is also gaining followers among athletes.
It consists of depriving yourself of food for more or less prolonged periods. Outside of these times, there are no restrictions on the types and amount of food eaten. There are several variations of intermittent fasting including, but not limited to, alternate fasting (every other day), modified fasting (reducing calorie intake on two non-consecutive days a week) and time-restricted eating (for example , fasting from 6 p.m. to 10 a.m.).
What are the effects on athletic performance? What are the advantages, practical aspects and risks to consider?
I am a dietitian-nutritionist, holder of a doctorate in nutrition from Laval University, and currently a postdoctoral fellow at the University of Quebec to Chicoutimi. This article was written in collaboration with Geneviève Masson, sports nutritionist, who advises high performance athletes at the Canadian Sport Institute Pacific and teaches at Langara College in Vancouver.< /p>
Variable effects on sports performance
During physical activity, the body mainly uses its reserves of carbohydrates, called glycogen, as an energy source. In a fasting situation, glycogen stores decrease rapidly and the body increases the use of lipids to meet its energy needs.
When fasting, glycogen stores decrease rapidly and the body increases the use of lipids to meet its energy needs. (Shutterstock)
The practice of intermittent fasting has been associated with a decrease in fat mass and the maintenance of lean mass in athletes. However, these changes do not always correspond to an improvement in sports performance, as evidenced by the contradictory results of several studies.
Several studies report unchanged aerobic capacity, measured by a VO2 max test. after intermittent fasting in well-trained elite cyclists and long-distance and middle-distance runners. In trained runners, there was no effect on running time (10km), level of perceived exertion and heart rate.
In addition, perceived fatigue and muscle soreness were increased in trained cyclists during Ramadan, which may be partly due to dehydration since fluids are also restricted during this period, when nothing can be consumed from sunrise to sunset. sun.
In the context of fasting, low glycogen (carbohydrate) stores can limit the performance of repeated intense efforts. In fact, there was a decrease in the speed of repeated sprints in active adults after fasting for 14 hours a day for three consecutive days.
Power and anaerobic capacity, evaluated at Help from the Wingate test (stationary bike test) was decreased after ten days of intermittent fasting in active students, while it was increased after four weeks in another study also in active students.
Men and women on a weight training program had similar gains in muscle mass and strength when they practiced intermittent fasting compared to a control diet. There was no significant difference in muscle power between active men who did or did not practice intermittent fasting. However, one study reported an increase in muscular strength and endurance in young active adults after eight weeks of resistance training combined with intermittent fasting.
Thus, the results vary greatly from study to study and are influenced by several factors, including the type of fast and its duration, the level of the athletes, the type of sport, etc. In addition, very few studies have been carried out in women and the absence of a control group in most studies makes it impossible to isolate the effect of intermittent fasting.
For the moment, it is therefore not possible to rule on the effectiveness of intermittent fasting in improving parameters related to sports performance.
The effects of intermittent fasting on sports performance, according to the current state of knowledge. (Bénédicte L. Tremblay)
Eating before and after training
Athletes who wish to resort to intermittent fasting must take into account several practical considerations. Is his training schedule compatible with this dietary approach? For example, does the period during which he is allowed to eat allow him to eat enough before physical exercise or to recover adequately after training?
And, not insignificant, what about food quality, knowing that an adequate protein intake is essential for the recovery and maintenance of lean mass in order to limit the negative impacts on performance.
Questioning the impacts — and reasons — of fasting
Intermittent fasting could induce too great an energy deficit for some athletes with high energy needs, including endurance sports athletes (running, cycling, cross-country skiing, triathlon, etc.) due to the volume of training. They can then suffer from the relative energy deficit in sport, which is a syndrome that affects in particular the secretion of hormones, immunity, sleep and protein synthesis. If the deficit is prolonged, adverse consequences on athletic performance ensue.
Intermittent fasting could induce an energy deficit that is too great for some athletes with high energy needs, including endurance sports athletes due to the volume of training. (Geneviève Masson), Author provided
It is also essential to question what motivates the adoption of a dietary practice as strict as intermittent fasting. Some people do it for religious considerations like Ramadan. Others are motivated to engage in weight control behaviors in hopes of achieving an “ideal” body. according to socio-cultural norms.
A recent study demonstrated that practicing intermittent fasting over the past 12 months was significantly associated with behaviors associated with eating disorders (overeating, compulsive exercise, vomiting, and laxative use). Although this study cannot determine whether it is fasting that causes eating disorders or if it is eating disorders that lead to fasting, it does highlight an associated risk of this practice.
A recent study demonstrated that the practice of intermittent fasting in the past 12 months was significantly associated with behaviors associated with eating disorders. (Shutterstock)
Finally, we must also question the impact of intermittent fasting on social interactions. The fasting schedule could limit participation in social activities involving food. What is the risk of negatively influencing the eating behaviors of other family members, especially children or adolescents who see their parents refrain from eating and skip meals?
Is this a good idea or a wrong-idea??
With such contradictory scientific data, there is no It is not possible at this time to comment on the effects of intermittent fasting on sports performance.
Further studies are needed before this practice can be recommended, especially for seasoned athletes. Moreover, the potential negative effects on other aspects of health, including eating behaviors and social interactions, are not negligible.
Bénédicte L. Tremblay, Nutritionist and postdoctoral fellow, University of Quebec at Chicoutimi (UQAC) and Catherine Laprise, Professor UQAC, Co-holder of the Quebec Research Chair in Sustainable Health and Director of the Intersectorial Center for Sustainable Health at UQAC, University of Québec à Chicoutimi (UQAC)
This article is republished from The Conversation under a Creative Commons license. Read the original article.