Thursday, June 7, 2012

Fasting and exercise performance

So being in the CrossFit world for many years, I've been bombarded with various nutrition regimens, Intermittent Fasting (IF), paleo, and the Zone Diet being the 3 main ones. I love CrossFit, but I got sick of the various nutrition regimens, because every other year it was something different (paleo is, in my opinion, the most important and valuable one, but more on that in another post!).

I dabbled with IF for a while, and it definitely did NOT work for me; I lost weight, and my performance suffered. However, I was curious if there had been research on what happens in the body during fasting and a bout of exercise. For my research paper in exercise physiology, I did a paper on Ramadan fasting and exercise performance (Ramadan had the most research on fasting and exercise performance). Obviously, not all of us will be engaging in fasting like in Ramadan, but the research was interesting in that it showed how fasting such as Ramadan fasting affects (or, as most of the research showed, does not change), exercise performance.

In the United States, Americans are bombarded by media that describes the numerous ways to exercise and lose weight; a number of these endeavors involve some sort of caloric restriction and/or moderate fasting, which many individuals find difficult to manage. On the other hand, in the Islamic religion, Muslims who choose to participate in Ramadan are required to fast fromsunrise to sunset for one month – abstaining not only from foods, but fluids as well. Athletes who choose to participate in Ramadan are of particular interest to researchers; with the increased amount of stress that the body is subjected to during athletic activities, the question arises whether,during Ramadan, people adhere to such a fasting protocol. In this review of the literature, studies conducted on various types of athletes are examined, as well as the various metabolic adaptations (if any) were present in the subjects, and whether exercise performance was compromised by the increased amount of stress involved in fasting itself.
Studies in Physically Active Men
Two of the studies looked at physically active men who did not engage in any formal sport. In one study, Trabelsi et al. analyzed the differences between aerobic training during the day during the fasted state, and at night, after the break of the fast. 19 physically active men were brought to the lab on 4 separate occasions: 3 days before Ramadan, the 15th day of Ramadan, the 29th Day of Ramadan, and 21 days after Ramadan; 10 were exercising in the fasted state (between 4 and 6 pm), and 9 in the fed state (between 9:30 and 10:30 pm). Sessions included one of cycling, running, and rowing. While in the lab, body composition, dietary analysis, urine specific gravity, serum glucose, blood glucose, uric acid, total cholesterol, triglycerides, urea and creatinine were measured and assessed. In the fasting group, urine specific gravity, renal function markers, sodium, chloride, urea, and uric acid all increased, which indicated dehydration; none of these factors increased in the fed group. HDL levels rose in both, and the fasting group also experienced a loss of body weight and body fat, while the fed group only experienced a decrease in body weight, although this lack of change of body fat could have been the result of human error in measurement, according to the researchers (Trabelsi et al., 2011).
On a different premise, Souissi et al. examined Ramadan’s effect on the diurnal variations in anaerobic performance. In this study, 12 physical education students were assessed for anaerobic power at 7 am, 5 pm, and 9 pm, 1 week before, the 2nd week of Ramadan, the 4th week of Ramadan, and 2 weeks after Ramadan. Participants were assessed via the force-velocity test, which is repeated bouts of 6 second all out sprints against resistance that increases until the subject can no longer maintain 100 revolutions per minute. Subjects were also assessed in the Wingate test. From the two tests, Ppeak, Pmax, and Pmean were calculated. Comparing the values before and during Ramadan, there was no significant difference during Ramadan for the 7 am tests, but the values were lower at 5 pm and 9pm during the second and fourth weeks of Ramadan. The results of this study suggest that Ramadan directly effects the circadian rhythm of anaerobic power, although other possible explanations were that the later times of day were just more fatiguing for the participants because they had been without food and drink for quite some time (Souissi et al., 2007).
Studies in Male Middle-Distance Runners
Chennaoui et al carried out a study in which they examined Ramadan’s effect on diet, sleep, mood, metabolic, hormonal, and inflammatory responses in middle distance runners who maintained their normal training volume during Ramadan. In this study, 8 runners performed an incremental running test to exhaustion on 3 separate occasions: 5 days before and days 7 and 21 of Ramadan; cortisol and testosterone levels were measured before and after the running test. Blood samples were also taken at 3 separate times (before, at the end of Ramadan, and after Ramadan).  The MAV (maximal aerobic velocity test) decreased at days 7 and 21 compared to the test before Ramadan; sleep and energy intake were also lower at day 21 than before, and fatigue had increased by the end of Ramadan. During the second blood test, IL-6, an inflammatory parameter, increased, melatonin decreased, and adrenaline and noradrenaline increased; these values all returned to normal after Ramadan had ceased. No body composition changes were seen during this time. The ratio of testosterone to cortisol was measured, because a value of 1 indicates a balance between anabolic and catabolic occurrences in the body; in this study, the ratio had decreased by the third week, followed by a decrease in the MAV test. This study concluded that Ramadan induced a decrease in aerobic capacity and increased pro-inflammatory responses in these athletes (Chennaoui et al. 2009).
Studies in Male Rugby Players
Rugby is a popular sport in Islamic countries, and athletes who choose to fast could be at greater risk for dehydration from the fasting. In one study, Rebai et al measured dehydration status in 12 male rugby players during rugby sevens matches (a 14 min game of rugby in which there are 7 players a side). The players performed 3 matches: 1 day before, at the end of the first week, and at the very end of Ramadan. Body weight was taken before and after matches, to determine fluid loss, as well as blood samples. By the end of Ramadan, increases were seen in resting hematocrit, hemoglobin, and plasma osmolarity values, compared to the beginning of Ramadan. After a match, hematocrit and plasma osmolarity saw increases at the end of Ramadan, which indicates acute levels of dehydration.  There was no change in the percentage of body water status markers, nor was there a significant change in total body water. A decrease in body weight was also seen, likely due partly to a decrease in water consumption as well as an increase in fat oxidation. Although the athletes exhibited signs of dehydration, a rugby sevens match does not exacerbate the magnitude of responses to matches of blood and body water status markers (Rebai et al., 2011).
Similarly, Bouhlel et al led a study to examine Ramadan’s effect on fuel oxidation during exercise. In this study, 9 male rugby players were tested on 3 separate occasions: before, during, and at the end of Ramadan. During this time, the players performed a submaximal cycle ergometry test that progressively increased loads corresponding to 20, 30, 40, 50, and 60% of Wmax. Substrate oxidation was measured via indirect calorimetry. At the end of Ramadan, decreases in body mass and fat mass were seen, with a preservation of lean tissue. Daily energy intake was reduced, but fat constituted a higher percentage of daily food intake. Hemoglobin and hematocrit levels were higher at the end, at both rest and after exercise. The researchers also saw an increase in fat utilization, demonstrated by an increase in the crossover point at the end of Ramadan (35% of Wmax compared to 30% at the end vs. beginning, respectively); the crossover point is the point in which carbohydrate becomes the primary energy source). LipoxMax, which is the point where the utilization of lipids is highest, was also higher at the end  (265 mg/min vs. 199 for end and beginning, respectively). Plasma glucose levels remained unchanged, which could be explained by glycogenolysis or gluconeogenesis. Although the results indicate a shift toward increased fat oxidation, RER was found to be extremely varied and individual, with one participant even seeing an increase in RER by the end of Ramadan. Nevertheless, this study demonstrated that Ramadan results in an increase in lipid oxidation and a decrease in body mass and fat mass (Bouhlel et al. 2006).
On a different note, Denguezli et al. measured parameters of insulin resistance in trained rugby players at rest and after aerobic exercise. 9 male rugby players were tested 1 week before, at the end of the first week, and during the fourth week of Ramadan; testing was done between 2-4 pm w/ last meal having been taken at 1 am the previous night. The players were tested on a progressive cycle ergometer test, which was the same as the preceding study. Various metabolic and hormonal parameters were measured at rest and after exercise. Daily caloric intake was greatly reduced during Ramadan. Fat intake did not change significantly, but fat constituted a larger percent of energy intake during Ramadan. Resting and postexercise triglycerides increased during Ramadan. Although there was a reduction in body mass and body fat, there was no change in adiponectin or leptin values (adiponectin is usually correlated with fat loss). The adiponectin:lepitin ratio can also provide a useful measure of insulin resistance, but no change was seen with this ratio. This suggests that the food restrictions associated with Ramadan do not disrupt this balance. It was also suggested that the rugby players saw an increase in fat oxidation, partly due to the increase in the percentage of calories coming from fat, which resulted in more lipid availability for oxidation. There were also no changes in levels of creatinine, which suggested that there was no protein catabolism, therefore demonstrating that fat loss occurred, but lean tissue was maintained (Denguezli et al., 2008).
Studies in Young Male Soccer Players
Soccer is one of the most popular sports in Muslim countries, and the majority of the research done on athletes partaking in Ramadan have been done on soccer players, many of them being youth players.  The majority of these studies saw similar trends in data. In a study by Zerguini et al., the researchers examined 4 teams during an 8 week training camp in which 64 members fasted and 36 did not. Zerguini et al. observed a small decrease in the body mass of the fasting group, and an RPE that indicated the fasting group was a little less ready to train; but none of the performance tests during the camp were affected by the fast, nor were biochemical factors; in fact, by the end of the 3rd testing session (which included soccer specific sports drills as well as shuttle runs), most of the performance tests had improved in the fasting group (Zerguini et al., 2008).  Similarly, Guvenc tested 16 young male soccer players during Ramadan for body composition and aerobic performance, and they found that body fat percentage decreased, but that BMI and fat free mass was relatively unchanged. These young soccer players also had a slight increase in their RPE scores, but blood lactate and heart rate during and after the incremental running test decreased by the end of Ramadan. These soccer players also saw improvements in their peak running and running velocity at the anaerobic threshold. There were also no changes in total body water and urine specific gravity, which indicates that the players were relatively hydrated (Guyenc, 2011).
These results were similar to Aziz et al. who tracked the National Under-18 soccer squad who were divided into both fasting and fed groups during a 4 week training period. The players were tested by the shuttle run, as well as soccer specific training four times per week; both fasting and non-fasting groups trained together, and it was found that there were no significant differences between the fasting and non-fasting groups in their RPE after exercise, nor their test performance before and after Ramadan; in fact, the fasting group was able to keep up with the non fasting group for the entire month. An obvious limitation of this study, however, was that other factors indicating performances, like heart rate and blood lactate and running speed were not measured (Aziz et al., 2011).
In terms of anaerobic capacity in young soccer players, Chtourou et al. tested 10 soccer players in the Wingate test at 7 am and 5 pm on three different occasions throughout Ramadan. Before Ramadan, peak power, mean power, and fatigue index were greater in the evening than in the morning, but these diurnal variations went away by the end of Ramadan. RPE was also higher in the evening by the end of Ramadan than before Ramadan. Similar to the study done by Souissi et al., this was thought to be due to a modification in the circadian rhythm during Ramadan (Chtourou et al., 2011).
Another interesting study done by Wilson et al. sought to see how the timing of sleep was altered during Ramadan, and how this affected practices in professional soccer players. 20 players were monitored over 8 weeks, and it was found that during Ramadan, the average bedtime was 4:26 am, compared to 1:07 am after Ramadan, and that sleep duration during Ramadan was greater (9 hours and 49 minutes and 8 hours during and after Ramadan, respectively). Practices were also shifted to later at night (8:30 pm) during Ramadan, as opposed to 5:30 pm after Ramadan ended. It was also found that there was a 2.7% loss of body mass during Ramadan, partly due to dehydration as indicated by an increase in urine osmolality. Peak core temperatures were also approaching hyperthermic levels, although the soccer players continued to train despite these increased stresses (Wilson et al., 2009).
In conclusion, the documented research on how Ramadan affects competitive athletes has conflicting results depending on the study. In general, the current research documents a variety of different types of athletes and also has a mixture of various parameters measured, including both physiological (hydration status, body composition, aerobic, anaerobic training, and more) and mental (RPE, for example); this variety is a strong point in the current research as a whole. All of the studies also had a control period (either before or after Ram
dan) in which to compare the results obtained during Ramadan. However, one major weakness of most of these studies is the absence of a true control group; only the studies done by Zerguini et al. and Aziz et al. had true, non-fasting control groups to compare values to. The majority of these studies would be much stronger if they had a control to compare their results too. In addition, there are no studies on women. Although most likely due to culture differences, it would be of use to obtain research studies that document female athletes, and to see how female athletes are affected by Ramadan in comparison to men. It would also be of use to conduct research on a variety of sports in addition to the ones present here; there is a lack of data on strength training and strength responses during Ramadan, which could be of use, especially to sports teams who strength train as part of their regular training regimen.
Although there are conflicting results, the majority of the research appears to demonstrate that as long as athletes maintain their normal hydration and caloric intake during the times that they are permitted to eat, there is not a significant decrease in performance. Because fat tends to constitute a larger part of the diet during Ramadan (Denguezli et al.), fat oxidation increases, and thus decreases in body fat are common, even though lean body mass is generally preserved. It could also be suggested that athletes modify their exercise or training regimens to right before the break of fast, or after the fast has already been broken, as this helps to alleviate the discomfort associated with not being permitted to drink or eat after exercise earlier in the day; it would be interesting to examine if shifting exercise to just before or after the break of fast lowers inflammatory parameters that were seen in the study by Chennaoui et al. For future research, more studies need to be done on women, and studies should aim to have a control group.