Achieving or maintaining a healthy weight is a balancing act. If we regularly eat and drink more kilojoules than we need for our metabolism, we store it mostly as fat. Most of the energy we use each day is used to keep all the systems in our body functioning properly. This is out of our control. However, we can make metabolism work for us when we exercise. When you are active, the body burns more energy kilojoules.
Our metabolism is complex — put simply it has two parts, which are carefully regulated by the body to make sure they remain in balance. They are:. Based on a moderately active person 30—45 minutes of moderate-intensity physical activity per day , this component contributes 20 per cent of our daily energy use. The BMR refers to the amount of energy your body needs to maintain homeostasis. Your BMR is largely determined by your total lean mass, especially muscle mass, because lean mass requires a lot of energy to maintain.
Anything that reduces lean mass will reduce your BMR. As your BMR accounts for so much of your total energy consumption, it is important to preserve or even increase your lean muscle mass through exercise when trying to lose weight.
This means combining exercise particularly weight-bearing and resistance exercises to boost muscle mass with changes towards healthier eating patterns rather than dietary changes alone as eating too few kilojoules encourages the body to slow the metabolism to conserve energy. Energy expenditure is continuous, but the rate varies throughout the day. The rate of energy expenditure is usually lowest in the early morning. Your BMR rises after you eat because you use energy to eat, digest and metabolise the food you have just eaten.
The rise occurs soon after you start eating, and peaks two to three hours later. This rise in the BMR can range between two per cent and 30 per cent, depending on the size of the meal and the types of foods eaten. Different foods raise BMR by differing amounts.
For example:. Energy used during exercise is the only form of energy expenditure that we have any control over. However, estimating the energy spent during exercise is difficult, as the true value for each person will vary based on factors such as their weight, age, health and the intensity with which each activity is performed.
Australia has physical activity guidelines that recommend the amount and intensity of activity by age and life stage.
Hormones help regulate our metabolism. Some of the more common hormonal disorders affect the thyroid. This gland secretes hormones to regulate many metabolic processes, including energy expenditure the rate at which kilojoules are burned. Thyroid disorders include:. Our genes are the blueprints for the proteins in our body, and our proteins are responsible for the digestion and metabolism of our food.
Sometimes, a faulty gene means we produce a protein that is ineffective in dealing with our food, resulting in a metabolic disorder. In most cases, genetic metabolic disorders can be managed under medical supervision, with close attention to diet.
The symptoms of genetic metabolic disorders can be very similar to those of other disorders and diseases, making it difficult to pinpoint the exact cause.
See your doctor if you suspect you have a metabolic disorder. Some genetic disorders of metabolism include:. This page has been produced in consultation with and approved by:. Content on this website is provided for information purposes only. Information about a therapy, service, product or treatment does not in any way endorse or support such therapy, service, product or treatment and is not intended to replace advice from your doctor or other registered health professional.
RMR accounts for up to 75 percent of the calories you burn each day. Knowledge of your individual RMR is a critical piece of information to appropriately establish daily calorie needs. Metabolic rate is traditionally assessed using either direct or indirect calorimetry. This minute screening uses indirect calorimetry which determines metabolic rate from the oxygen consumption of an individual.
So it's not surprising that many people think of it in its simplest sense: as something that influences how easily our bodies gain or lose weight.
That's where calories come in. A calorie is a unit that measures how much energy a particular food provides to the body. A chocolate bar has more calories than an apple, so it provides the body with more energy — and sometimes that can be too much of a good thing. Just as a car stores gas in the gas tank until it is needed to fuel the engine, the body stores calories — primarily as fat.
If you overfill a car's gas tank, it spills over onto the pavement. Likewise, if a person eats too many calories, they "spill over" in the form of excess body fat. The number of calories someone burns in a day is affected by how much that person exercises , the amount of fat and muscle in his or her body, and the person's basal metabolic rate BMR.
BMR is a measure of the rate at which a person's body "burns" energy, in the form of calories, while at rest. The BMR can play a role in a person's tendency to gain weight. For example, someone with a low BMR who therefore burns fewer calories while at rest or sleeping will tend to gain more pounds of body fat over time than a similar-sized person with an average BMR who eats the same amount of food and gets the same amount of exercise.
BMR can be affected by a person's genes and by some health problems. It's also influenced by body composition — people with more muscle and less fat generally have higher BMRs. But people can change their BMR in certain ways. For example, a person who exercises more not only burns more calories, but becomes more physically fit, which increases his or her BMR.
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