What is your metabolic rate? Metabolism refers to the biochemical reactions involved in converting foodstuffs into other forms of energy. These are then ultimately used by the body for fuel. This fuel is used for all types of physical work, i.e. moving and lifting, but it is also used in more subtle ways that we don’t necessarily think about. Producing and nurturing offspring obviously requires a huge amount of additional energy, as does the constant maintenance of our own bodies; breathing, pumping blood around the body, and chewing and digesting food just to name a few.
Metabolic rates explained…
Put simply then, our metabolic rate is the amount of energy expended by an organism during a given time period. In humans we usually measure this daily and not surprisingly it can differ significantly, between individuals. For example, a muscular, elite male athlete will need and burn significantly more energy than a sedate, lean female. This means there is no ‘normal’ metabolic rate so to speak, as so many factors can affect it. As a general rule however, the greater the mass of an organism, the higher that organisms’ metabolic rate will be.
At rest, meaning in periods of inactivity, the rate is known as the basal metabolic rate (BMR) which is low compared to when the body is undergoing activities like exercise. During this resting state the body only needs to use energy in line with processes above i.e. to keep vital organs such as the heart, lungs and brain functioning properly and can range from between 60%-80% of calories consumed.
How can you measure your Metabolic rate?
Metabolic rate can be measured in a few different ways. These include measuring oxygen consumption, and carbon dioxide or heat production. We also know there are various states which cause metabolic rate to change. For example, if you’re ill with a fever, your metabolic rate will increase. This is in order to produce the additional heat which makes your body hotter. Additionally, what is also well documented is that your metabolic rate is always lowered during active weight loss, no matter the method, as this is your body’s way of trying to conserve energy.
Can you help speed up your metabolic rate?
There’s a lot written about foods that are purported to slow down or speed up your metabolic rate. Unfortunately the science behind these claims is poor. For example, green tea is often touted as a fat burning chemical, but in terms of making a difference to the actual numbers of calories burned, it’s negligible. The one notable exception is that per gram, protein is recognised to require more calories to break it down, than does fat or carbohydrates. Plus coupled with proteins satiating effects, you will often see protein presented as a nutrient of choice for dieters.
Do some people have slower metabolic rates than others?
Many people with problems of excess weight may often state that they have slower metabolisms, but the opposite is true. The bigger you are, the faster your metabolic rate. This is because a larger body needs more energy (calories) to function than a smaller one. A big, heavy Rolls Royce needs a bigger engine and has a higher fuel consumption than a diminutive Mini. Fatter people burn more energy than thinner people of the same height. This is because the heart, lungs and other organs have to work significantly harder. Equally, numerous studies show that ‘naturally skinny’ people actually consume significantly fewer calories than bigger people of the same height.
So what happens during and after a diet, will my metabolism be damaged?
In the first couple of weeks of a diet, your metabolic rate drops temporarily by around 15% as the body uses up stored fat as fuel. When you come off the diet, metabolic rate makes its way back up to ‘normal’. However, that ‘normal’ won’t be as high as it was when you were bigger. This is because a lighter body needs less energy to function than a heavier one. This explains why it’s so easy to regain weight after dieting. It means you need to rethink your approach to eating. Cut down your ‘usual’ intake to match your lighter body’s reduced energy requirements. Your metabolisms not wrecked – it’s just your ability to judge food intake that’s out of kilter.