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October 22, 2003
Typical
menus at McDonald’s, KFC and Burger King contain
65 per cent more calories per bite than standard British meals,
making it far too easy for customers to overindulge without
realising it.
The high “energy density” of junk food — the
amount of calories it contains in relation to its weight — throws
the brain’s appetite control system into confusion, as
this is based on the size of a portion rather than its energy
content.
The critical role of energy density in obesity has been revealed
by Andrew Prentice, Professor of International Nutrition at
the London School of Hygiene and Tropical Medicine, and Susan
Jebb, of the Medical Research Council Human Nutrition Centre
in Cambridge.
In a study published in the journal Obesity Reviews, they calculated
the average energy density of menus at McDonald’s, KFC
and Burger King, using nutritional data from the fast food
chains’ websites.
The average energy density of these restaurants’ meals
was 1,100 kilojoules (263 calories) per 100 grams (4oz), 65
per cent more than the density of the average British diet
and more than twice that of a recommended healthy diet. This
means that a person eating a Big Mac and fries would consume
almost twice as many calories as someone eating the same weight
of pasta and salad.
Professor Prentice said that the human appetite encouraged
people to eat a similar bulk of food, regardless of its calorific
value. This left regular consumers of fast food prone to “accidental” obesity,
in which they grew fat while eating portions they did not consider
large.
Professor Prentice added: “Since the dawn of agriculture,
the systems regulating human appetites have evolved for the
low-energy diet still consumed in rural areas of the developing
world, where obesity is almost non-existent. Our evolved system
of appetite control is completely unpicked by the junk food
diet.”
When fast food is eaten often, even small miscalculations of
portion size can have major effects, the study found. If a
person eats 200g (7oz) extra of fast food with a density of
1,200kJ per 100g just twice a week, he or she would consume
an extra 250,000kJ (59,808 calories) a year. This is enough
to put on almost 8kg (17.6lbs) of fat.
Fast food outlets should reduce the energy density of their
menus as well as their portion sizes, the scientists said.
The
Times
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