18 BBC SCIENCE FOCUS MAGAZINE COLLECTION
More than half a billion people in the world are obese.
Increasingly sedentary lives and a shift in diet are to
blame. The South Pacific island of Samoa has the
highest proportion of obese people – a whopping 74.
per cent are considered obese. In f ac t , South Pacif ic
nations reign in the top 10 – only Kuwait is not in the
region. Elsewhere around the world, there is a direct linkwith income – the prevalence of obesit y is four times
higher in high-income countries than low-income ones.
African and Asian countries generally have very low
obesity levels. Less than two per cent of the populations
in Vietnam, Bangladesh, Nepal, India, E thiopia, Eritrea,
Madagascar and the Democratic Republic of the Congo
are considered obese.HOW FAT ARE WE?
KEY
Percentage
of population> 30%10-19.9%NO DATA20-29.9%< 10%FACT
2.8 million
people worldwide
die each year as
a result of being
overweight or
obeseFACT
Obesity is
prevalent in the
Middle East due
to an increasingly
sedentary lifestyle
and junk foodFACT
5% of children
globally are
considered
to be obeseFACT
Two times more
women (9.9%) are
extremely obese
than men
(5.5%) in the USTo be de f ine d a s
obese, you need to have
a body mass index (BMI)of over 30kg/m (^2). BMI is
calculated by dividing your
weight by the square
of your height.
The past few years have seen growing interest in
the idea that our gut bac teria play a crucial role in
regulating weight, and killing them off with
antibiotics is causing obesity.
The mos t recent evidence is f a scinating but
inconclusive. Studies in prestigious medical journals
have produced contrasting results. One found that
three courses of antibiotics before the age of two
was associated with increased risk of early
childhood obesity, while the other found that
exposure to antibiotics in the first six months of life
was not associated with early childhood weight gain.
Yet recent research is indicating a link bet ween gut
f auna and our body ma ss index. People with higher
levels of Christensenellaceae bac teria – one in 10 of
us – appear less likely to put on weight than those
with lower amount s. Scientis t s from King’s College
London have found that levels of this bac teria are
partly genetically determined.
According to Dr Giles Yeo, who investigated the
possibility of microbial transplants to cure obesity,
this new field is important and requires research.
“But I have yet to see convincing evidence that there
are lean bacteria and obese bacteria,” he says.
Verdict: More research needs to be done, but
our gut bacteria may affect how readily we
put on weight.
ARE ANTIBIOTICS MAKING US FAT?