The Science behind Weight Loss.

Understanding the science behind weight loss and what is happening to your body during exercise is important to achieving your weight loss goals! Weight Loss is one of the major reasons people exercise. There are a few who genuinely exercise because they actually enjoy the effects of pushing their bodies to the point of exhaustion, however the majority of people do not look forward to this kind of activity. This is usually due to the fact that to lose weight whilst exercising requires the participant to exert tremendous energy to accomplish their desired results.

Now before we continue to swimming to slim, I believe it is important to understand the science of weight loss and have a basic understanding of what is actually happening to our bodies during exercise. Too many people are trying to lose weight without knowledge of the fundamental scientific reasons as to why they are actually losing weight. To have an idea of when, how and why our bodies shed weight during exercise is a good place to start and I believe it is as important as the procedures required to lose weight.

Food Intake.

To understand the basics behind weight loss and weight gain, we must first understand a basic law of physics. Momentarily consider the human body as a machine and apply this law, “Energy Output from a machine equals Energy Input”.  Now consider if our energy input (food) is greater to the Energy output(exercise). This usually results in weight gain as we are generally eating too much and exercising too little. Obviously the body operates differently to a machine, but it needs fuel in the form of food, and it expends energy when we walk, talk and sleep. When our energy input(food) is greater than our daily total of energy expired the body stores the excess energy as glycogen and fat. Glycogen is generally stored in our muscles and liver and is mobilised at initial stages of energy output(exercise), whereas fat can only be utilised after your glycogen levels have been used up, therefore you are required to exercise for considerable time to see the benefits of the chemical reaction which converts body fat to energy and hence weight loss.

Basal Metabolic Rate (BMR)

The energy required to keep the body functioning when it is resting and sleeping is called the BMR. Our personal BMR differs depending on our age, gender and weight, and can be  calculated to predict how much more we need to eat when we are awake and working or how much less we need to eat to lose weight.

Our BMR changes throughout life and is affected by age, illness, hormones, diet and exercise.

If we choose to participate in a sensible weight loss diet  we usually find that :

  • When our calories are first restricted through the process of a healthy diet, that weight loss is slow. We should never consider undertaking a starvation approach of  dieting as the benefits of crash dieting are usually non productive and can be quite harmful to the body if continued for prolonged periods.
  • Once weight loss is achieved, there will be a small fall in Basal Metabolic Rate (or BMR), The BMC rate is affected by the your weight. The lighter you are the less your BMR. The greater your weight the higher your BMR. As weight loss continues, BMR continues to fall, so the myth that overweight people have a slower metabolism is not true. They have a slightly raised BMR to cope with the maintenance of a larger body mass.


Exercise increases our BMR. It is important to try not to eat soon after exercising until the BMR recovers and returns to normal. The increase BMR is one reason for our appetite increasing after exercise. If we can resist the urge to eat while our body recovers from the physical activity it has undertaken, we can capitalise on EPOC, or Excess Post-exercise Oxygen Consumption. It is imperative that a combination of  sensible dietary restrictions and exercise is continued as this is the basic building stones to healthy weight loss. Be sure not to  ruin all the hard work you have put in by  immediately replacing all the calories burned off by consuming extra food or drink.

 BMRThe Science behind Weight Loss.

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