Page 16 - BBC - The Scientific Guide to a Healthier You
P. 16
“If you want to
sustain your
weight loss,
the worst thing
you can do is
try and starve
yourself for
three weeks”
DO CRASH DIETS WORK?
It depends what you mean by ‘crash diet’. There is evidence that “If you want to sustain your weight loss, the worst thing you can
supervised food replacement diets work very well for many people. do is try and starve yourself for three weeks,” he says. “I think
But what about the more DIY crash diets that claim to make your people have to find some balance to lose weight long-term.”
weight plummet? Diets like the cabbage soup diet, the grapefruit In particular, we have to address how crash diets generally make
diet, and juicing and cleansing diets? us feel hungry. Dr Yeo’s research examines how the brain responds
The evidence behind these is currently slim. But there is less to hormones and nutrients that are released from the gut into the
scientific opposition to losing weight quickly than there used to blood. These reflect the body’s nutritional status and the brain
be. Australian research has indicated not only that more people turns them into what we experience as ‘fullness’ or ‘hunger’.
achieve their weight loss goals if they lose weight fast, but also “One of the universal truths of weight loss is that if you want to
that losing weight quickly doesn’t mean you’ll regain it quickly eat less then you have to have a strategy to make you feel more full,
too. Rapid weight loss can motivate people to stick with some otherwise you are simply fighting hunger for the rest of your life,”
programmes, the researchers suggest. Dr Yeo says. “What we now know is that the longer something takes
But maintaining a healthy nutritional balance while on these to be digested, the fuller it makes you feel – because as food goes
diets can be a problem: advice from the NHS is still that “crash diets down the gut, different hormones keep being released, most of
make you feel very unwell and unable to function properly… crash which give us a feeling of fullness. That’s why high-protein diets can
diets can lead to long-term poor health.” work, because protein is more complex than fat or carbs, and goes
And both our biology and lifestyles may condemn many extreme further down the gut before it’s broken into its constituents.”
crash diets to failure. Dr Giles Yeo, principal research associate at
Cambridge University’s Institute of Metabolic Science, specialises in Verdict: Crash diets are not nutritionally balanced and will
the molecular mechanisms underlying the control of food intake. make you feel awful.
16 BBC SCIENCE FOCUS MAGAZINE COLLECTION
