'Chubby children are not that way because they're greedy or lazy'

Andrea Burgener on the big, fat weight loss myths we buy into

Is there anything as sad as seeing a chubby child being teased?

Well perhaps watching that child being forced into endless physical activities which make them feel chubbier and even less confident, by well-meaning parents and teachers who've been conned, like all of us, into believing that weight loss or gain is about calories and that these calories can — in any meaningful way — be burnt off through exercise.

It's time we stopped torturing children, and accepted that this theory has always been plain wrong.

Our weight has extremely little to do with our activity level or with calories.

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Many of us do know that it's the type of calories, not the calories per se, that determine weight. But for some reason, we don't follow the next logical step: the big idea we're not living by is that our weight is largely determined by our hormones.

In other words it's about biology, not physics. The false idea that "energy in versus energy out = your weight" is so nicely simple.

Many dieticians will tell you that "it's a thermodynamic principle". Hah, science stuff! It must be right. But the principle (energy can't be destroyed) only holds water in a "closed system with thermal equilibrium", and that is definitely not our bodies.

Anyway, the law in no way says "energy in = energy out". If this "absolute" theory were true, we'd all have to do a lot of maths at every meal to neither fade away or become obese.

Clearly, this is ludicrous. If this exact relationship exists, how do teenage boys lie around like sloths, eat five times the amount other humans do, and stay as thin as rakes? Yep, hormones.

block_quotes_start How do teenage boys lie around like sloths, eat five times the amount other humans do, and stay as thin as rakes? Yep, hormones block_quotes_end

Why do people who frequent gyms tend to be leaner? Because they tend to be health-conscious, looks-conscious, disciplined people, and often genetically predisposed to be lean.

But how can we expect this sort of discipline from children? It's plain cruel.

Children definitely need to exercise, but it should be fun, it should be affirming, and it's for a whole different set of reasons.

Chubby children are not that way because they're greedy or lazy. It's the adult world's fault that the wrong food is shoved in front of them.

An average well-meaning lunch box might look like this: a sweetened mini-yoghurt, an apple, a sandwich, a "health-bar" or muffin.

Or to put it another way, four different shapes and textures of carbohydrate. Carbohydrates raise insulin. Raised insulin in the blood tells your body to hold onto fat. When your body holds onto its fat storage, you're perpetually hungry and have little energy.

There is no better reading on the issue than Why We Get Fat: And What To Do About It by science journalist Gary Taubes, published by Alfred A Knopf.

• This article was originally published in The Times.