An additional 20 percent admitted to having had too much to drink at such a soiree.

London - Slimmers be warned. Having a few drinks can wreak havoc with your waistline – even if you’ve switched to a low-calorie tipple.

Just one boozy session a week can lead to us taking on enough calories to put on 2lb (about a kilogram), say experts.

And most of the flab comes from food we polish off when we’ve been drinking, rather than from the alcohol itself.

Feasting on fatty takeaways after the pubs and clubs have shut and combating a hangover with a full English breakfast can see men alone put away an extra 5 000 calories.

Even if we otherwise stick to a healthy regime, a regular once-a-week night out could make us pile on two stone (about 13kg) over a year.

Slimming World, which commissioned a survey into drinking habits, says more needs to be done to highlight alcohol’s role in weight gain and wants cans and bottles to clearly display calorie counts.

The YouGov poll of more than 2 000 Britons reveals how drinking is contributing to the UK’s obesity crisis, which is now the worst in Europe. It found that the average man reaches “tipping point” – the moment we start to drink and eat more than intended – after 10.5 units of alcohol, or about four pints of beer. The extra drink after this point, combined with fatty food such as chips, kebabs, pizzas and hamburgers, leads to him packing away an extra 6 940 calories.

This is more than three times the recommended daily intake for men and the equivalent of 38 bags of crisps. Drink adds 1 795 calories, while 3 126 comes from food eaten that evening. Eating unhealthy food the next day adds another 2 025.

The female “tipping point” is eight units – just two to three large glasses of wine. Beyond that, women consume an extra 5 725 calories – almost three times the daily recommended intake and the equivalent of nearly two dozen jam doughnuts.

Almost 60 percent of those surveyed said they pass their tipping point at least once during a typical weekend. With 3 500 calories roughly equal to a 1lb (450g) gain in weight, millions of Britons could be piling on the pounds because of nights out. Inactivity while nursing hangovers adds to the problem.

Dr Jacquie Lavin of Slimming World said alcohol leads us to make unhealthy choices because it stimulates appetite and lowers inhibitions. - Daily Mail