How bodies are producing energy When you exercise and move about, the body needs to produce more energy than it would at rest to fuel muscle contractions, heart to pump blood and the lungs to take in oxygen and expel waste. The bodies version of fuel is called adenosine triphosphate or ATP. ATP is produced from fats, carbohydrates, protein and alcohol. ATP is then broken down to produce energy, a bi-product of this process is heat and is the reason our body temperature rises during exercise. The amount of available ATP the body has can only produce enough energy for a few seconds while exercising. So as we require more energy, more ATP must be produced by breaking down more fats, proteins, alcohol and carbohydrates. The different foods which we consume are broken down into different units and stored within the body in different ways; proteins are stored as amino acids, fats into fatty acids and carbs into glucose, fructose and galactose. Alcohol cannot be stored within the body so must be converted in energy to dispose of it. While this is happening the body doesn’t use CHO and fats to produce energy, thus promoting fat storage and weight gain. Depending on the action and the energy requirement the body will utilise different energy stores through 3 processes to produce the required ATP. Which process is used is dependent on the intensity of the exercise and how fast ATP is required to be continually produced. From our knowledge of the different types of muscle fibres, we know there is fast and slow twitch fibres, and what actions target each type of fibre. Depending on the type of fibre being recruited, decides on what mechanism of ATP production is put into place. For fast actions where fast twitch fibres are recruited, two mechanisms can be utilised, these do not require oxygen to be present in the process and are solely reliant on glycogen and creatine stores. These processes can only sustain energy production for a short period of time, while slow twitch fibres utilise only one method of ATP production in which oxygen is combined with glycogen and fat. This process can be sustained over long periods of time and is brought into use when the other two methods have been exhausted. The body has enough glycogen stored to fuel the body through intensive exercise for two hours, after this time blood glycose and fat is broken down for energy. When trying to lose weight it is important to create a slight kcal deficit. This forces the body to oxidise fat stores to sustain ATP production through this third production method, but requires carbohydrate to bind with the fat and oxygen. If the kcal deficit created is too much, muscle will also be broken down for energy, resulting in lower metabolic rate. When people talk about metabolic rate they are describing the rate of calorie expenditure which is required by the body to sustain vital functions on tickover. There is a direct relation to metabolic rate and a person’s weight. The more someone weighs, the more energy is required for the body to sustain all its vital functions. Muscle requires more energy than fat does, so the more fat free mass a person has, the higher there metabolic rate will be. Calories are the amount of energy stored within foods. High calorie deficits are something which can occur in faddy diets, where the initial weight loss is normally due to loss of water, rather than an actual reduction of body fat. When exercising for weight loss cardio training is extremely important for creating this kcal deficit, but equally important is resistance training to deter muscle breakdown. So while exercise is one way to create this calorie deficit for weight loss, and balanced diet and slight reduction in calorie intake along with exercise is the best method for weight reduction for long periods of time.