The study, published in BMJ Medicine, found that among the official public health definitions* used to identify and regulate food and drink products in the UK, each varied widely in what proportion of processed and ultra-processed products was classed as unhealthy, while systems such as traffic light labels failed to identify more than half of these unhealthy packaged foods.
When the Eatwell Guide — a set of government recommendations for nutrient, food and drink intake — was used to define unhealthy food, it classified over 98% of ultra-processed products and 95% of processed products sold in the UK as unhealthy.
By contrast, the voluntary green, amber and red traffic light labelling on the front of packaging identified fewer than half (48.2%) of those foods as unhealthy.
The high fat, salt and sugar (HFSS) definition used by the Food Standards Agency Nutrient Profiling Model (FSA-NPM) to restrict the advertising and promotion of unhealthy foods identified just over half (57.6%) of the same foods as unhealthy.
As a result, the researchers suggest that inconsistencies in labelling and regulation may lead consumers to buy food and drink products which have high levels of saturated fat, salt and sugar without realising they are unhealthy.
The authors conducted a cross-sectional analysis of a representative database of 262 processed and 1,636 ultra-processed food and drink items available across the UK.
They then compared the proportions of processed and ultra-processed products identified as unhealthy by FSA-NPM, the traffic light system and new Nutrient Profiling Models aligned with the Eatwell Guide.
Professor Chris van Tulleken (UCL Infection, Immunity and Transplantation), the study's senior author, said: "This study shows that the UK food environment is saturated with products that make it hard for consumers to eat a diet in line with UK government advice. The reason such products are so dominant may be because existing labelling and regulation systems fail to identify them as unhealthy.
"If these products make up the majority of a person's diet, as they do in the UK, there is a significant risk of consuming more sugar, salt and saturated fat than the Eatwell Guide recommends, even if someone fastidiously avoids red traffic lights, and HFSS products.
"This itself would be difficult as traffic lights are voluntary and the HFSS definition is hidden from consumers."
Lead author Sam Dicken (UCL Epidemiology and Health Care) said: "Our analysis shows that tools for regulating healthy and unhealthy foods in the UK are inconsistent.
"For example, traffic light labelling showed that 48% of ultra-processed products surveyed are unhealthy, and the FSA-NPM showed that 57% of ultra-processed products surveyed are unhealthy. But nutrient profiling models based on UK government guidance, the Eatwell Guide, indicated that between 91% and 98% of ultra-processed products surveyed are unhealthy.
"Current food and drink regulatory tools do not capture products with an excess content of harmful nutrients, but UK dietary guidance does."
Some of the food products which would be classified as having high levels of fat, salt and sugar under the Eatwell Guide include canned pasta in tomato sauce, macaroni cheese made from packet mix, and fat-free probiotic yoghurts. These products are not identified as being unhealthy under traffic light labels or the HFSS definition.
Conversely, foods such as nuts or whole fruit may be flagged as being high in sugars or fats by traffic light labelling, despite being encouraged as part of a healthy diet by the Eatwell Guide.
Co-author Dr Dolly van Tulleken, Visiting Researcher from the University of Cambridge, said: "This study reveals how confusing and incoherent the UK government's definitions of unhealthy food are.
"Products classified as unhealthy by one system are healthy under another. A single, unified system for categorising food and drink products as unhealthy using existing UK dietary guidance, is much needed, both for consumers and regulation.
"This must be developed independently of food and drink industry influence. This would help to close regulatory loopholes and address the inconsistency of front-of-pack 'traffic light' labels and FSA-NPM."
Co-author Dr Adrian Brown (UCL Division of Medicine) said: "This study highlights the need for clearer, more consistent food classification systems that better align with the UK dietary guidelines to help consumers make informed choices about food and drink."
Study limitations
The authors note that while their study identifies a representative selection of processed items to compare the performance of different models, it does not suggest this would be an exact list of foods which would be subject to regulation, nor the specific regulatory approaches that should be used. These approaches should be developed independently of food industry influence.
Additionally, as the analysis focuses on processed and ultra-processed products it does not test minimally processed foods. There may therefore be additional scope for future studies around this food area.
*For this study, researchers evaluated the Eatwell Guide, the Food Standards Agency Nutrient Profiling Model, the front-of-pack multiple traffic light system, and used the Nova classification of food processing to identify processed and ultra-processed food in the UK.
