A study has claimed that drivers who eat a big meal risk falling asleep while they are driving.
The study suggests that a big lunch,even without the effect of alcohol,can make it harder to concentrate on the road,leading to potentially dangerous mistakes.
Young men who did a test drive in a simulator after a fatty and sugary meal were more likely to drift into another lane than those who had a lighter lunch.
While the effect of alcohol on motoring skills has been much researched,this study is one of the first to look at the impact of a full stomach.
Twelve healthy young men attended Loughborough Universitys sleep research centre for a lunch of beef lasagne and a toffee yoghurt.
Half were given diet versions,totalling 305 calories,while the others ate the normal versions,which were much fattier and full of carbs,and had a calorie count of 922.
All normally slept well but had only slept for five hours the previous night,something the researchers say would not be unusual.
After lunch,they were put in a driving simulator and tasked with a two-hour-long,dull,monotonous drive along a dual carriageway with long straight sections and gradual bends.
Young men were chosen because males under 30 are particularly likely to fall asleep at the wheel.
Those who had the heavy lunch were more likely to drift into the other lane.
They started off not too badly,making just as many mistakes as the light lunchers for the first half hour but after that there was no doubt that they were sleepier.
Worryingly,the men did not seem to realise that they were becoming weary.
Our study utilised palatable ready meals of the type that people might realistically have for lunch, the Daily Mail quoted Researcher Louise Reyner (CORR) as saying.
The mechanisms underlying why a heavy lunch enhanced aspects of sleepiness must remain a matter for speculation.
However,high fat intake does elevate blood levels of the hormone cholecystokinin,which does increase lassitude, she said.
She added that big lunch appears to exacerbate the effects of a poor nights sleep,and having even just one glass of wine or beer with the meal could make things much worse.