Researchers at Cambridge University say that people who eat too much do so because portion sizes are often too large.
The study, published in the Cochrane Database of Systematic Reviews, found that by removing large portions from the diet completely, energy intake could be reduced by 16 per cent among British adults.
The researchers pooled data from studies which examined the diet of 6,711 volunteers, and determined that people consistently eat more when offered larger portions and plates. This suggests that by just reducing portion sizes, calorie intake could be reduced significantly. Until now the role of portion size in overeating has not been proved, the researchers say.
The study’s co-author, Dr Gareth Hollands, says:
‘It may seem obvious that the larger the portion size, the more people eat, but until this systematic review the evidence for this effect has been fragmented, so the overall picture has, until now, been unclear. There has also been a tendency to portray personal characteristics like being overweight or a lack of self-control as the main reason people overeat.’
‘In fact, the situation is far more complex. Our findings highlight the important role of environmental influences on food consumption. Helping people to avoid ‘overserving’ themselves or others with larger portions of food or drink by reducing their size, availability and appeal in shops, restaurants and in the home, is likely to be a good way of helping lots of people to reduce their risk of overeating.’
The researchers say there is a lack of evidence to suggest that self-imposed short-term changes in food consumption are likely to become permanent. They say the key could be in forcing manufacturers to limit portion sizes or ensuring that supermarkets reverse the current trend of offering bulk buy deals, instead making smaller portions more economically attractive.