Professor Paul Dobson, from the University of East Anglia (UEA), led a three-year study of consumer behavior toward food and the impact on overeating and food waste. He concluded that unhealthy foods receive too much promotion from supermarkets and said the food industry must do more to promote healthy living.

"It is simply irresponsible for supermarkets to overly promote foods with high sugar and fat content," he said. "The food industry must play a much greater role in promoting healthy diets.

"Food producers can do more by reducing the fat, sugar and salt content of processed foods, while food retailers can ensure that healthy and nutritious choices are available and affordable to all consumers and that they practice responsible marketing."

Dobson said that if retailers and producers did not take responsibility, regulation might be needed.

Special offers are worth more than £50 billion in sales to supermarkets and account for over a third of all consumer spending in the United Kingdom.

The research team analysed weekly price and nutrition data of a full range of food and drinks products sold over a year by four U.K. supermarkets -- Tesco, Asda, Sainsbury's and Ocado.

They found a bias toward sugary products for price promotions, while straight price discounts were on average more skewed toward unhealthy products. Special offers also tended to be slanted toward more unhealthy products, especially those with high sugar content. However, multi-buys were on average more biased toward healthier items.

"While price promotions can offer savings for consumers they may not be so good for our waistlines and health," he added.

"With almost a quarter of the population classed as obese, overeating and food waste are serious concerns for modern society."