Nutrition and sport study

We will talk about an experiment where we compared two diets and performance. We have used the high fat and high carbs diets, using a maximal O2 uptake test (VO2 max). This is an indicator for cardio-pulmonary fitness and breathing at sea level  has the normal value of 61 ml/min/kg, using a maximal power of 310 watts.

On high carbs diet the time to exhaustion was 65 minutes and the glucose level in the blood after the exercise was 5.6 mmol/liter.

On high fats diet the time to exhaustion was 45 minutes and the blood glucose level after the exercise was 4.4 mmol/liter.

We know that performance is influenced by genetics (trainability and age), training (psychology, physiology and technique) and health (sickness, injury, fatigue and nutrition). Glucose as fuel has the advantage of being locally available (stored in the liver and muscle as glycogen) and has more power than the fat, but we got a limited storage (2000 kcal). Fat as fuel is a huge resource (at least 100.000 kcal), but is slow to mobilize and has less power than the carbohydrates. For high intensity exercise, glucose is ideal, for endurance exercise, fat is better. It is good to know that we can exercise for a bit over one hour is we have full glycogen stores.

Strategy for endurance exercises: we should have the glycogen stores completely filled, ingesting more carbs if the exercise is taking more than 45 minutes. You have no real benefit if you have carbs before the 45 minutes of exercise if you started fully loaded with glycogen.

Strategy for strength or power exercises: glycogen stores should be filled prior to the training or competition, you should also aim for 1.4 grams of protein per kg consumption, avoiding prolonged catabolic periods (do not fast or avoid food). If you are vegan or vegetarian, in order to achieve muscular physique, you should choose the right protein sources (beans, soy etc). Do not forget about the fluid intake during exercise, if it is cold you do not need it for very short bursts, but if it is warm and you are sweating a lot, take care of your re-hydration. Ketosis as a diet works well for medium intensity and long interval trainings (it is a high fat/low carbs diet).

Exercise benefits are important: we can lose weight if it is done long enough, but sometimes it is not apparent, as we lose fat and gain muscle, it is increasing our physical activity and functionality (especially the endurance or resistance training) and it is improving our health parameters (lowering high blood pressure, increasing the plasma HDL level, lowering the triglycerides level and improving insulin sensitivity). Talking about exercise, we need to mention supplements and ergogenic aids.

The ergogenic aids can be classified as:
-metabolic fuels (energy drinks and gels), which are good for endurance training, higher than 45 minutes;
-caffeine and caffeine related stimulants, good to exercise longer (endurance training);
-creatine monophosphate, good for high intensity training as is maintaining ATP levels up (fuel for muscle);
-anabolic substances (protein, aminoacids and other ones that will be not mentioned, as they are illegal in most countries);
-rehydrating fluids, like water, with or without electrolytes.

I mentioned ketosis earlier, i will try to explain this concept a bit more. Ketosis is defined as the formation of ketone bodies in our system. There are three ketone bodies: acetone, acetoacetate and beta-hydroxybutyrate, all of them made from fatty acids in the liver when the supply of fatty acids is highly elevated, as in the case of  prolonged fasting and uncontrolled diabetes. Normally the concentration of ketone bodies in our blood is very low, but if we try a ketogenic diet, with a high fat/low carbs content, even if some of the ketones are lost via urine, the concentration in our blood can reach 0.5 mmol or even higher if it is combined with exercise. The advantage of the ketone bodies is that even if the liver produce ketones, cannot use them, but to supply glucose to the brain during prolonged fasting, the glycogen stores are depleted after one day, and when proteins are used to convert into glucose, we experience muscle loss, this is the moment when our survival mode is activated, and the liver take the fatty acids and it will convert it into ketone bodies, delivering them to the brain as a fuel. Stored fat is used indirectly by the brain, and the need to degrade proteins is reduced.

However, the ketogenic process is dangerous during uncontrolled diabetes (diabetic keto-acidosis) or  alcohol abuse (alcoholic keto-acidosis). High levels of ketones will lower the blood Ph, being a life threatening condition. Carbs based diets leads to undetectable levels of ketones, but one day of fasting will result in 0.5-1 mmol ketosis. Prolonged fasting will increase it up to 6 mmol, and diabetic ketosis is bigger than 20 mmol.

The glycogen is prioritized to extra-hepatic tissues, the brain and the other tissues take out their share first, then the muscle is filled, followed by the liver. Both stores of glycogen to be empty is a very rare occurrence, but can happen if you do heavy training in the morning without breakfast. Our glycogen stores are mostly filled up, unless we do intense exercise or low carbs dieting or spend too much time without eating. The liver store is fully depleted after 24 hour fasting. Muscle stores are filled first in case of low carbs diet, the liver store being minimized.