Classification of junk food

What constitutes unhealthy food may be confusing and, according to critics, includes elements of class snobbery, cultural influence and moral judgement. For example, fast food in North America, such as as hamburgers and french fries supplied by companies like McDonald's, KFC and Pizza Hut, are often perceived as junk food, whereas similar meals supplied by more up-market outlets such as California Pizza Kitchen or Nando's are not, despite often having the same or worse nutritional content. Some foods that are considered ethnic or traditional are not generally considered junk food, such as falafel, gyro, pakora, gyoza or chicharron, though all of these foods have little nutritional value and are usually high in fat from being fried in oil. Other foods such as white rice or roast potatoes are not considered junk food despite having limited nutritional content compared to wholegrain foods. Similarly, breakfast cereals are often regarded as healthy but may have high levels of sugar, salt and fat.

Some types of chips/crisps that are said to be "junk food" may actually be partially harmful because they may contain polyunsaturated and monounsaturated fats. It should also be understood that the detrimental effects of the empty calories may outweigh the benefits of the unsaturated fats. These foods tend to be high in sodium, which may contribute in causing hypertension (high blood pressure) in people sensitive to its effects with an existing electrolyte imbalance or inability to excrete sodium properly.

In the United Kingdom, the Food Standards Agency (FSA) do not use the term "junk food", and describe food as "HFSS" (high fat, sugar or salt) instead, based on a nutrient profiling model. They state that "HFSS foods can form part of a balanced diet, but research shows that children's diets contain too much fat (especially saturated fat), salt and sugar, and not enough fruit and vegetables.