Do you know about your body’s metabolism?

We’re always told that if it sounds too good to be true, it usually is. So how can you possibly burn kilojoules, and even fat, without hitting the gym?

While it’s generally true that the more you move and the higher the intensity, the more kilojoules you’ll burn, you’d be amazed what you can achieve without all the sweating and grunting. In fact, you can even burn kilojoules in your sleep.

A key el­e­ment in weight man­age­ment is un­der­stand­ing your me­tab­o­lism – the body’s way of get­ting the en­ergy it needs from food.


A lot of people talk about their metabolism as if it’s a muscle or organ they can somehow control. But in reality, the term refers to a series of chemical processes in each cell that turn the kilojoules you eat into fuel to keep you alive. It’s the culmination of different tissues with different needs and how many kilojoules it takes to keep them functioning. The body’s major organs – the brain, liver, kidneys and heart – account for over half of the energy burned at rest, while fat, the digestive system and especially the body’s muscles account for the remainder.


There are three main ways you burn energy: a) the basal metabolism, which is the energy used for your body’s basic functioning while at rest; b) the energy used to break down food, also known as the thermic ­effect of food; and c) the energy used in physical activity. One very underappreciated fact about the body is that your resting metabolism accounts for a huge amount of the total kilojoules you burn each day. Physical activity, on the other hand, accounts for a tiny part of your total energy expenditure – about ten to 30 per cent (unless you’re a professional athlete or have a highly physically demanding job). 


It’s true that two people with the same size and body composition can have different metabolic rates. One can consume a huge meal and gain no weight, while the other has to count kilojoules.

Researchers have been able to find some predictors of how fast a person’s metabolism will be. These include: the amount of lean muscle and fat tissue in the body, age and genetics (though researchers don’t know why some families have higher or lower metabolic rates). Gender also matters, since women with any given body composition and age burn fewer kilojoules than comparable men.

You can’t easily measure your resting metabolic rate in a precise way. There are some commercially available tests, but the best measurements come from research studies that use expensive equipment. However, you can get a rough estimate of your resting metabolic rate by plugging some basic variables into online calculators, such as age, height and weight. These will tell you how many kilojoules you’re ­expected to burn each day, and if you eat that many and your weight stays the same, it’s probably correct.


The effect happens gradually, even if you have the same amount of fat and muscle tissue. So if you’re 60, you’ll burn fewer kilojoules at rest than you did when you were 20.

This continual ­decline starts in young adulthood – and why this happens is another metabolism question researchers haven’t answered. Why do your energy needs go down as you age, even if you keep everything else pretty much the same? That’s one of the bigger ­mysteries.


There’s a lot of hype around ‘speeding up your metabolism’ and losing weight by exercising more to build muscle, eating different foods or ­taking supplements. But it’s a myth.

While there are certain foods – like coffee, chilli and other spices – that may increase the basal metabolic rate just a little, the change is so negligible and short-lived, it would never have an impact on your waistline.

Building more muscles, how­ever, can be more helpful. Here’s why: one of the variables that affects your resting metabolic rate is the amount of lean body mass you have. At any given weight, the more muscle on your body, the higher your metabolic rate. That’s because muscle uses a lot more energy than fat while at rest.

So the logic is, if you can build up your muscle, you’ll have a higher resting metabolism and will burn the fuel in your body more quickly. But there’s a caveat.

If you have more muscle, it burns fuel more rapidly. But that’s only half the question. If you do gain more muscle and effectively speed up your metabolism, You have to fight the natural tendency to want to eat more as a result of your higher metabolism.


While it’s extremely hard to speed up the metabolic rate, researchers have found there are things that can slow it down – like drastic weight-loss. For years, researchers have been documenting a phenomenon called ‘metabolic adaptation’. As people lose weight, their basal metabolic rate actually slows down to a greater degree than would be expected from the weight loss. To be clear, it makes sense that losing weight will slow down metabolism. Slimming down generally involves muscle loss, which, in turn, means the body doesn’t have to work as hard to keep running. But the slowdown after weight loss, researchers have found, often appears to be substantially greater than makes sense for a person’s new weight.

Once you gain weight and keep the weight on for a period of time, the body can get used to its new, larger size. When that weight drops, a bunch of subtle changes kick in – to the hormone levels, the brain – slowing the resting metabolism and having the ­effect of increasing hunger and decreasing satiety from food, all in a seeming conspiracy to get the body back up to that set point of weight.

Metabolism plays a part but the simple fact is that everything you do requires energy. This includes obvious things like walking, cycling and lifting weights, but also things like playing with the kids, gardening and washing the dishes. To your body, it’s all basically the same – using muscles to move your body parts. And to those active muscles, it’s all about grabbing energy from the food and drink you’ve consumed to power those moves. Your heart and lungs chip in too, making sure your muscles have enough oxygen to burn that energy. So while organised exercise is great, lots and lots of everyday movement is great too. You might have heard it referred to as ‘incidental exercise’, and it’s a great way to get lots of bonus physical activity into your life. JUST MOVE is the mantra. 

So keep moving and stay healthy!

Check out my related post: What is Omada and how it helps fight Diabetes?

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6 thoughts on “Do you know about your body’s metabolism?

  1. ◇ – Diamond Hard – ◇

    ◇ An Acceptance of The Power of Energetic Activity, especially Evolution; which is Impossible if We ARE BEING Distracted by Nutrition and Exercise…a Physiological Sensation may have be for many different reasons; for example Throwing Up could be Eating/Drinking too much/the wrong thing, Pregnancy Morning Sickness or a “Gym” Junkie Pushing Their Body Too Far

    ◇ – Diamond Hard – ◇


    Liked by 1 person

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