Consumers were losing trust in brands that claimed they were 'fat-free' or 'low in calories', said an Engage Research study.
Many felt food companies were misleading them about the healthiness of a product by using labels to mask other content information such as high sugar, salt and artificial flavouring levels, it added.
"It seems that many consumers believe manufacturers have taken liberties in the past in their use of the term 'healthy' and now many simply don't believe it," said Engage Research director Andy Barker.
This scepticism could also tarnish people's perceptions of products that currently had a trusted 'healthy' brand image with customers, he warned.
But Barbara Gallani, director of food safety and science at the FDF, denied manufacturers made misleading claims. "Nutritional claims on food products are strictly regulated," she said.
The European Commission is expected to approve a long list of health claims next July after it abandoned its policy of monitoring manufacturers claims on a batch-by-batch basis.