Compared to a 6-day carbohydrate-rich diet, the oxygen uptake increases more slowly after a fat-rich diet at the start of an effort. Also, after a high-fat diet, more oxygen is needed for the same effort and the heart rate is approximately 10 beats higher.
Nutrition for endurance athletes
In recent years, much more scientific attention has been paid to low-carbohydrate diets for endurance athletes. One of the major champions of this movement is Prof. Tim Noakes from South Africa. Whereas Noakes used to be a strong proponent of carbohydrate-rich food with endurance performance, he is now trying to convince more endurance athletes that fewer carbohydrates can lead to better performance. Instead of carbohydrates, athletes should eat more fats and proteins. Researchers from Canada have now investigated the effect of eating a high-fat diet on oxygen intake at the start of and during exercise. This is important for, among other things, the emergence of the so-called oxygen deficit. Read more about the oxygen deficit in this summary.
Lots of fat vs. lots of carbohydrates
Eight healthy men aged 24 years with a maximum oxygen intake of 45 ml / kg.min participated in this study. They were given a diet for 6 days that consisted of 75% fat, 20% protein, and 5% carbohydrates. On days 5 and 6 of this high-fat diet, the test subjects had to cycle for 6 minutes at 20 watts during an exercise test. Immediately afterward, they had to cycle for 8 minutes with a capacity that corresponded to 80% of the capacity at which they produced more lactic acid than they degraded.
This protocol was repeated three times with 30 minutes of rest in between. After the last day of the high-fat diet, the subjects were given a carbohydrate-rich diet. This consisted of 10% fat, 10% protein, and 80% carbohydrates. The subjects again had to do the exercise test discussed earlier on days 5 and 6 of the diet. The calorific value of both diets was the same.
The results show that the oxygen uptake at the start of the effort increases more slowly after the high-fat diet than after the carbohydrate-rich diet. This creates a greater oxygen deficit. Besides, the oxygen uptake during rest and exercise was higher after the high-fat diet than after the carbohydrate-rich diet. In other words, the same effort required higher oxygen consumption. It also turned out that the heart rate was 10 beats on average after rest and during exercise after the high-fat diet.
This study by Raper and colleagues shows that a high-fat diet has a negative influence on the rate at which the oxygen intake increases during the start of the exercise. The consequence of this is that a relatively large oxygen deficit arises. Since it also appears that the same amount of effort requires a higher oxygen consumption after a high-fat diet, it must be concluded that a carbohydrate-rich diet is a right choice for delivering good endurance performance.
Journal Appl. Physiol., #10,1152 / japplphysiol.00456.2014. Writers Paterson DH, Peters SJ, Heigenhauser GJF, Kowalchuk JM