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If you increase physical activity levels, then you will burn more energy. When the body requires energy, it can obtain it from carbohydrates, fats or proteins. Each of these macronutrients will provide energy at different times during physical activity.

Fats and carbohydrates – are used for providing most of the energy.
Proteins – only tend to play a role in energy provision during very long bouts of exercise when glycogen stores are depleted.

Fats can never be used completely independently of other macronutrients. Whatever the exercise, both fats and carbohydrates will be used to provide energy, but the percentage of each used will change depending on, the Intensity of the exercise, duration of the exercise and fitness levels.

Your body burns fat for fuel to meet low energy needs. As exercise intensity increases, the percentage of carbohydrate used for energy increases and the percentage of fat used for energy decreases. When undertaking aerobic exercise (that is exercise that increases the body’s need for oxygen such as cycling, swimming, dancing etc.), and the duration of the exercise increases, the body starts to use more fat as fuel and less carbohydrate.

You can optimise fat burning for fuel by controlling your diet and planning exercise around your meals. Controlling your carbohydrate intake, avoiding sugars and simple carbohydrates and sticking to complex carbohydrates and starches will help keep your insulin levels steady and avoid insulin spikes. Carbohydrates and sugars are converted into glucose; insulin is a hormone that transports glucose to the muscles for energy. When insulin and glucose are abundant, your body doesn’t burn fat for fuel, it uses the carbohydrate, as it’s easier to convert to energy. Bring your insulin levels down before low-intensity exercise by lowering carbohydrate intake a few hours before.

Roughly 50% of you daily diet should consist of complex carbohydrates, which should include, vegetables, fruit, grains and starches. If you do not maintain adequate carbohydrate intakes and stores (as glycogen) through a well balanced diet, then once any glycogen/carbohydrate stores have been used up, the body is forced into using other sources of fuel alongside fat. In these circumstances, the body would use protein, in the form of muscle. In these circumstances where carbohydrate is not readily available, and protein is being used instead, the body does not function so well. In terms of exercise performance, it may lead to earlier than normal fatigue and slower recovery after an exercise session. Take a protein supplement that includes branch-chain amino acids before exercise to prevent muscle loss during exercise and combine with resistance training.

Resistance training will increase the body’s muscle mass and the basal metabolic rate (BMR). However, resistance training is a form of anaerobic exercise and so does not use fat as a fuel when undertaken on its own. But, because it increases the body’s BMR it can help the body to burn more calories over a longer period. For this reason, to maximise the use of fat as a fuel, it is recommended that some resistance training be undertaken alongside aerobic exercise.

Perform a low-intensity aerobic exercise with large muscle groups for at least 45 minutes, because your body begins burning fat for fuel only after approximately 20 minutes of continuous activity. Each pound of fat contains 3,500 calories, and low-intensity aerobic exercise, such as walking, burns around 400 calories per hour. Keep your pulse within 50 to 75 percent of your maximum heart rate. Subtract your age from 220 to find out your MHR (max heart rate)

A point to remember, any activity will help reduce body fat providing that, throughout the day an overall calorie deficit has been produced. Never forget the key to long-term fat reduction is negative energy balance.

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