Television adverts for McDonald's healthier Happy Meal deals fail to encourage children to choose food that is better for them and instead promote a general preference for fast food, academic research suggests.

The menu choices of children aged seven to 10 who watched a series of adverts for meals in which carrots and apple could replace french fries were not significantly calorifically lower than they otherwise might have been. The children exposed to adverts for the Happy Meals were, though, more likely to express a liking for McDonald's and fast food in general. The regulator Ofcom judges whether food companies can advertise to children on the basis of the nutritional value of the products without taking into account the boost adverts bring to fast food brands as a whole.

Dr Emma Boyland, of Liverpool University, who carried out the study, said the research into the choices of 59 children, six of whom were overweight and five obese, raised questions over whether the big fast food brands should be allowed to advertise to children. Shadow public health minister Luciana Berger has previously proposed an overhaul of the rules.

Last week researchers at the Institute for Health Metrics and Evaluation at the University of Washington claimed that British girls were the fattest in Europe – with 29.2% of those aged under 20 being overweight and obese. It was also claimed that more people in the UK were obese or overweight than at any other time in the last three decades

In Boyland's study, half of the children watched 10 programmes with adverts for McDonald's Happy Meals, while the other half watched the same number of programmes with toy adverts. Of those children who had watched the McDonald's adverts, 84% subsequently said that they had a liking for fast food. This compared to 76% of those who watched the toy adverts. The calorific content of the choices made by those who had seen the Happy Meal adverts, in which healthy choices are celebrated, were not significantly different from the other group.

Boyland said: "I think my research suggests that the advertising is not driving healthier choices. The children didn't see healthy options and think 'I will have organic milk and carrot sticks'. The vast majority chose fries and a soft drink. But we did ask them how much they liked fast food in general and after seeing the McDonald's adverts their liking for fast food went up. My interpretation is it drives increased liking of fast food, not healthier food choice."

Boyland added: "It's a big debate then about whether we should allow fast food giants to advertise healthy options. If it is advertising healthy stuff, that should in theory be a good thing, but if the brand is so well known for fast food and, on the whole, people are buying unhealthy options from there, is that something we should be cracking down on?"

Rules drawn up by Ofcom prohibit advertisements for food and drink products high in fat, sugar and salt to be shown in and around programmes specifically made for children. The regulations were first introduced in 2007 and extended in 2008. However, a further analysis by Boyland suggests that the regulatory regime, described by the government as the most stringent in the world, is not protecting children.

During 1,931.5 hours of TV watched by children, from Peppa Pig to The X Factor, Boyland recorded 56,162 adverts – a rate of 29.1 an hour. There were 6,664 food and beverage adverts in the study period, broadcast at an average rate of 3.5 an hour. Fast-food items were the most heavily advertised foods (15.2%). Boyland said: "The aim of the regulations is to reduce the exposure to those sort of adverts and impact on diet. Our data suggests that this has not really happened."

Boyland said that another problem was that children's programming, during which fast food adverts are not allowed, was defined by the proportion of girls and boys who watch rather than by the number. She said: "So there will not be advertising during SpongeBob Square Pants, which will attract a 100% child audience of say 100,000 children. However, such advertising is allowed during The X Factor with, for example, a 10% child audience, equating to a million children. A bus can be driven through the loopholes."

McDonald's was not available for comment.