Uncategorized

When To Fuel And What To Fuel With

Why Is Fueling Important?

If you want to take your exercise performance to the next level, you must consider what you are eating, before, during, and after your exercise session. There is plentiful evidence to suggest that the timing of macronutrient (carbohydrates, proteins, and fats) intake can optimise both your exercise performance and recovery, keeping you energised throughout your workout and fresh for the next session.

Carbohydates

Carbohydrates make up ~50% of our daily calorie intake and are an important energy source during exercise, functioning to delay the onset of fatigue, meaning you can exercise at a higher intensity for longer. Whilst the body does store carbohydrate, these stores are limited (around 80-100g glycogen in the liver, 300-400g glycogen in muscle, and 20g glucose in the blood). Quite simply, you cannot perform if you are in a state of inadequate energy, so a high-carbohydrate diet helps to maintain muscle glycogen stores.

When exercising, you primarily use muscle glycogen as fuel. Prolonged exercise (~120 mins) can utilise all available glycogen stores, therefore if you are exerting yourself for this duration, say a long walk, it would be beneficial to consume food rich in carbohydrate to allow you to continue without feeling sluggish. For exercise durations of 1-2 hours, it has been advised that you should have around 30g/h carbohydrates. Feeding during exercise helps to maintain blood glucose levels and delay the onset of fatigue, and research has found that consuming a carbohydrate source which elevates glycogen content may delay fatigue by ~20% in endurance exercise lasting >90mins.

After exercise, it is recommended that you consume a source of carbohydrate as soon as possible; this is because the rate of glycogen synthesis is more rapid at this time (glycogen synthesis being the production of glycogen from glucose released from food following carbohydrate breakdown). The recommended intake is to consume 1-2 g/kg/BM (~50-100g) carbohydrate within the first hour post-exercise. If carbohydrate is limited, the body turns to protein breakdown in muscle in order to provide energy, and when using protein as an energy source, the body is depleting itself of vital building material.

Fats

Fat intake should account for 20-25% total energy intake to provide energy and maintain essential fatty acid and liposoluble vitamin requirements. Around 500g of fat is stored within muscle along with 7-10kg and 9-20kg of fat stored in adipose tissue in males and females respectively. 

A diet rich in fat will increase endogenous fat availability during exercise, allowing the body to increase fat oxidation and spare carbohydrate stores. However, higher fat diets have generally been shown to reduce exercise performance, particularly during high intensity exercise which rely on carbohydrate oxidation. 

Whilst there is no performance advantage to increasing fat consumption, fat adaptation and glycogen restoration is a favourable metabolic change.

Protein

Protein is the body’s building block and therefore a critical component of cells and tissues with many functions. Sources of high quality proteins include: eggs, milk, meat, poultry, fish, cereals, grains, and legumes. 

Unlike carbohydrate and fat, there is no significant reserve of body protein for use as an energy source. When using protein as an energy source, the body resorts to muscle protein breakdown (the degradation of whole proteins back to constituent amino acids) so the body is depleting itself of vital building material.

If weight training, partaking in gym classes or high intensity training, protein requirements are increased due to the accretion of lean muscle mass. For increased muscle growth, muscle protein synthesis must be greater than muscle protein breakdown (muscle protein synthesis being the creation of new proteins from amino acids and the driving force behind exercise adaptation). Whilst there is limited evidence to suggest any beneficial effects of consuming protein during exercise, ample evidence has shown that protein synthesis is maximised if a protein source is ingested 3 hours post-exercise. Generally, the anabolic response of muscle to ingestion of animal protein is greater than the response for plant proteins, resulting in increased muscle mass and strength during training. 

Read More