who struggle to lose weight, it has always made sense to blame a
In my work
as a diet doctor and nutritionist, I hear this excuse all the time
to explain away everything from middle-age spread to the fact that
their best friend eats twice as much, but stays effortlessly slim.
It’s not that
they are overeating, they insist, it’s because their body doesn’t
burn up calories as efficiently.
But what is
the real truth about the link between your metabolic rate – that
is, the amount of energy used up by your body just to keep your
heart beating, your blood pumping and so on – and weight gain?
Does a slow
metabolism automatically mean you will end up overweight? To find
out, I have tackled seven of the most common myths about metabolism.
people eat huge amounts and won’t get fat
This is so
widely believed and yet so very far from the truth. If you have
a lower than average metabolism, you might need fewer calories than
some others for your body to carry out all the basic functions.
But we’re only
talking about the calorie equivalent of a small latte or a small
piece of cheese on a cracker per day.
doesn’t explain why your friend seems to get away with eating a
side order of chips when you can’t.
is not that much higher than yours. The real reason she doesn’t
put on weight and you do is simple. She almost certainly doesn’t
eat as much food as that at every meal.
scientists agree these days that everyone who overeats will gain
weight and so this super-skinny friend of yours will be cutting
back on other meals and snacks to make up for the occasional indulgence.
I have conducted
food trials where we have enlisted ‘naturally skinny’ volunteers
to increase their calorie intake and they really struggled to overeat
at every meal.
Left to their
own devices, their instincts were to skip a meal or go light on
supper to balance out their intake.
helps boost metabolism
exactly true either. It is certainly correct that resistance exercises
such as free weights and gym machines build muscle, but muscle actually
has quite a low metabolic rate and gaining a whole kilogram of muscle
in the gym (which is a lot) would still add only ten calories –
equivalent to half a teaspoon of sugar – to your metabolic
rate, a day.
causes a drop in metabolic rate
We though we
knew the answer to this about 20 years ago, but the researcher who
drew this conclusion was subsequently prosecuted for fabricating
his metabolism data and spent time in jail.
What we do
know is that the final phase of the menstrual cycle in young women
increases metabolic rate by about 5 per cent, making them super-hungry,
and often with cravings for high-calorie treats.
So it’s quite
likely the hormonal changes brought on by the menopause reverses
this monthly rise. But it accounts for only a relatively small drop
in terms of the calories the body needs to function – equivalent
to a typical biscuit, in fact, per day.
have a faster metabolism than women which protects against weight
It is certainly
true that men have a higher metabolism than women by about 300 calories
a day. But while it used to be true that women gain more weight
as they age, men have done a remarkable job catching up in recent
years, so this higher metabolism doesn’t automatically protect men
against weight gain.
Men need to
keep an eye on calorie intake, too, if they want to stop piling
on the pounds.