People who gobble down their food and eat until they feel full are three times more likely to get fat compared with people who eat slowly and modestly.
So say Japanese researchers in a study that suggests shifting patterns of behaviour, driven by the advent of fast food and cheap food, are widely to blame for the obesity pandemic.
Osaka University's Hiroyasu Iso and colleagues recruited 1,122 men and 2,165 women aged between 30 and 69 and asked them to closely track their eating habits and body mass index (BMI), a benchmark of obesity.
Around half of the men, and just over half of the women, said they ate until they were full.
Just under half of the men, and a little more than a third of the women, said they ate quickly.
Men and women who ate until full were twice as likely to be overweight compared with counterparts who did not eat until full.
Those who ate both quickly and to satiety were three times likelier to be overweight.
"The combination of the two eating behaviours had a supra-additive effect on being overweight," the team say in their paper, published online Tuesday by the British Medical Journal (BMJ).
The study distinguished between people who ate until full and those who reported binge-eating.
Intriguingly, it found those who ate until full had in fact a higher calorie intake than those who gorged.
In a commentary, also carried by the BMJ, Australian nutrionists Elizabeth Denney-Wilson and Karen Campbell suggested that the drive to eat quickly is a genetic survival mechanism -- humans are hardwired to overconsume energy when it is available.
This mechanism has run into problems, though, with food that is cheap and instantly available and eaten swiftly, they argued.
"It may be that the changing sociology of food consumption, with fewer families eating together, more people eating while distracted (for example, while watching television), and people eating 'fast food' while on the go all promote eating quickly," said Denney-Wilson and Campbell.
"Furthermore, the increased availability of relatively inexpensive food, which is more energy-dense and served in substantially larger portions, may promote eating beyond satiety."