eating before training
The sympathetic nervous system
The sympathetic nervous system (SNS) controls fat oxidation (breakdown) in the body. Insufficient food and participating in exercise activates the SNS.
When you exercise in a fasted state the effects on cellular messengers (cyclic AMP and AMP kinase) are increased causing greater fat burning. Consuming a meal, particularly containing carbohydrates, will inhibit the SNS and in actual fact triggers the parasympathetic nervous system (PSNS), which promotes energy storage. This anabolic effect is of course the opposite of the catabolic effect we want. It is clear why a lot of people recommend training in a fasted state, as it appears to be beneficial for fat burning.
So why do YBP recommend eating before training?
The majority of fuel utilised during moderate to high intensity training will come from both glycogen stored in the muscle and liver, and fat stored in fat cells (adipose tissue) in a fed state. When our stores are full and not depleted we have enough energy to keep us going for 1-2 hours of intense exercise, and 3-4 hours of moderate training.
Blood sugar levels drop about 25 minutes into a workout. This is not a problem if you have plenty of stored glycogen to be broken down (glycogenolysis) and released as glucose into the bloodstream. If you are training in a glycogen depleted state symptoms such as dizziness, faintness, nausea or lightheadedness may occur. The best way to boost your metabolism over a 36-hour period is to perform high intensity exercise, but this method of training may be hard in a fasted, energy depleted state.
The body continually adjusts its use of fat and carbohydrate for fuel depending on a variety of factors such as exercise intensity, duration, fuel stores and fitness levels. It is theorised that if you burn more carbohydrate during exercising eventually you will burn a greater amount of fat in the post-workout period and vice versa. The high intensity training required to burn carbohydrates will inevitably create a post exercise metabolism boost causing a higher amount of fat to be burnt.
Fat loss should be assessed over days, not exclusively that hour at the gym. There has been plenty of research to show that fasted exercise utilises more fat during training, compared to fed state exercise. The trouble is that the exercise required to boost the metabolism and create the appropriate hormonal response (an increase in testosterone and human growth hormone), has to be high intensity, and little fat can be burned at this intensity. Only stored or recently consumed carbohydrate, or protein taken from muscle converted into glucose can be used.
It is true that fat is released into the bloodstream during high intensity training for oxidation, and more so in a fasted state. Lactic acid levels rise during this type of training, and lactic acid blocks the uptake of circulating fat into the cell. You then have a lot of extra fatty acids floating around in the blood that can't be used by working muscles. This fat will be restored in fat cells, in a process called re-esterification. The point here is that it is not the fat that is burned during the workout, but the metabolic boost gained from this type of training that we are trying to create, increasing the amount of fat burned for the next 1-2 days.
You can only really utilise fats at lower intensities. The trouble is you don’t get the increased metabolism and hormonal benefits at low intensities. Studies have shown that there is no difference in the amount of fat burnt in a fed or fasted state when exercising at a low intensity. Although it was shown that after 90 minutes there was increased fat burned in the fasted participants.
How to increase your metabolism
So if you want to burn a greater amount of fat you would have to exercise on an empty stomach for at least 90 minutes to get the fat burning benefits. At YBP we advise taking the shorter high intensity option for fat loss. This system has a metabolism boosting effect. This increase in metabolism is due to EPOC (excess post-exercise oxygen consumption). It is believed that training in this way will increase the metabolic rate by 15% over a 24-hour period up to 36 hours. In this period the body will use an increased amount of fat for energy, as it is the preferred fuel at low intensities i.e. when at rest, at home etc. As the intensity of the session drops, so too will the lactic acid levels allowing the fatty acids in the blood to be utilised by the cell. That’s why YBP has incorporated a lactic acid removal period in the middle of your interval programme, to oxidise some of the circulating fat. Training your body in this way regularly makes it more efficient at burning calories and generating energy. This is due to an increase in the number of mitochondria (the energy powerhouse in the cell). It has been shown that eating before exercise promotes the increase in EPOC.
The drawbacks of fasted exercise
Fasted exercise can have a detrimental affect on your body. Studies have shown that exercising in a fasted, glycogen depleted state has a catabolic effect on muscle. Protein losses can exceed 10 percent of the total calories burned over the course of a one-hour cardio session more than double that of training in the fed state.
Although at YBP we don’t advise it, certain body types, Mesomorphic, mesoendomorphic and endomorphic could potentially train in a fasted state. These body types have a higher proportion of muscle and ability to build muscle easily, reducing the worry of muscle breakdown. But training in a fasted state for ectomorphic and ectomesomorphic body types is never advised.
What to eat before training
It has been shown that consuming whey protein prior to exercise, elicits better results than using other forms of protein. It is thought the anti catabolic and anabolic signalling effects of the branch chain amino acids (BCAA) found in whey are responsible for this improvement. A 48 hour increase in resting metabolic rate of up to 6.5% has also been seen in the study participants consuming whey prior to exercise.
Amino acids from protein also have a carb sparing effect. When training at high intensities glycogen stores run low, and contrary to popular belief, the body does not switch to using fat for fuel. At these intensities protein is converted to sugar (gluconeogenesis), as fat cannot be oxidised (burnt) fast enough to keep up. So even if you are on a fat loss programme, amino acids will help you hold onto muscle tissue and keep metabolic rate up.
Check your nutrient table for your personal recommended amounts of carb and protein before training.