We all assume millennials are obsessed with avocado and acai berries.

But research suggests that they may not be splashing out on healthy brunches as much as we think - because they are worried the food is too expensive.

Despite the stereotype that they are a health-conscious generation, 25-34 year-olds were more likely than any other age group to say that they struggle to eat healthily because the foods cost too much.

The survey, carried out by insurers Aviva, found that more than three quarters of young people were interested in eating more healthily but found themselves unable to afford the food.

Women were slightly more likely than men to say it was a problem, with almost 80 per cent stating that they struggled to afford healthy food, compared to 75 per cent of men.

Among those aged over 55 the proportion was just 54 per cent.

Dr Doug Wright, the organisation's medical director, said the data "goes against the view that this is a generation who are juicing, detoxing and taking up all the latest healthy eating plans."

Young people also said they starved themselves during the day to "save up" calories for a big night out.