FIRST there was passive smoking. Now there鈥檚 鈥減assive overeating鈥�. It could partly explain the explosion in obesity in richer countries, say two researchers who hope their work will jolt governments into taking action, such as banning junk-food ads aimed at children.
One of the reasons people are getting fat is not because they are eating too much but because the food they eat is too rich, suggests Andrew Prentice of the International Nutrition Group at the London School of Hygiene and Tropical Medicine. We may taste the difference when we eat energy-rich food but our bodies do not take this into account, he says, so we eat as much as if it were low-energy food. 鈥淭he high energy densities of many fast foods challenge human appetite-control systems with conditions for which they were never designed.鈥�
In the mid-1990s, for instance, Prentice allowed groups of volunteers to eat as much as they liked. Those given food with a low energy density lost weight, but those on foods with a high energy density put on as much as 65 grams of extra fat a day.
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Now he and Susan Jebb of the Human Nutrition Research Centre in Cambridge, UK, have surveyed fast food companies to find out how energy-dense their foods are. 鈥淚 was astonished to see the average energy density of a burger, which is about 1200 kilojoules per 100 grams of food,鈥� Prentice says. The typical energy density of the British diet is around 650 kJ/100g, and our bodies probably evolved to cope with an energy density of just 450 kJ/100g.
In Obesity Reviews (vol 4, p187), Prentice and Jebb calculate that if someone overconsumes twice a week by 200 grams of fast food 鈥� about one burger 鈥� they could add up to 8 kilograms of body fat a year. 鈥淲e must do something, and stopping junk-food ads to children is an obvious place to start,鈥� says Prentice.
Junk food is increasingly coming under attack. Earlier this year, it was claimed that fast foods can be addictive (New 杏吧原创, 1 February, p 26). In the US, people who blame their ill health on fast food have attempted to sue McDonald鈥檚. And the UK is considering banning food ads aimed at children.