WHAT WE GET WRONG ABOUT METABOLISM

Weight loss feeling harder than it should? Your body isn't broken, but the old advice about how it spends energy might be

- By Dr Adam Collins

If you've ever struggled to lose weight, chances are you've blamed your metabolism - that mysterious phenomenon we're told keeps some people effortlessly slim while making weight loss an unwinnable battle for others. But that's not really how the body works - it's a warped version of the story that leaves out the parts that matter most for fat loss.

For starters, metabolism is more than just 'how many calories you burn'. It's the vast network of chemical reactions inside your cells and tissues that power everything you do. Still, most of us shrink it down to a single number: the calories burned at any given time.

That's where 'metabolic rate' comes in the go-to measure of how 'fast' your metabolism is running. In simple terms, it's the energy you use just lying still, the bare minimum your body needs to 'keep the lights on'.

Many people think it's slim individuals who have a 'fast' metabolism, which allows them to burn more calories without effort. In reality, it's actually larger bodies that have the 'faster' metabolism. Metabolic rate is mostly driven by body size - the more there is to maintain, the more energy the body uses.

That said, body weight alone is a very crude measure. Two people might weigh the same, but how that weight is made up - fat vs muscle - can make a big difference to their metabolic rate. This is because it's the fat-free (or lean) mass, that demands most of our energy.

And within that lean mass, your organs are the true powerhouses. The liver and brain account for around half of your body's resting energy needs, and even the kidneys need close to 20 per cent. Skeletal muscle is less metabolically active than your organs (about 20 times less, gram for gram), but because there's so much of it, muscle still makes up a big slice of energy use at rest.