They are thought to account for around 25-60% of daily energy intake in many countries.
One study, led by the University of Navarra, in Spain, involved nearly 20,000 adults, with an average age of 38, who were asked to complete detailed questionnaires about their daily habits.
In addition to their potential negative effect on weight gain detailed earlier this month, ultra-processed foods may increase risk of developing both cerebrovascular and cardiovascular disease.
Researchers at NutriNet Sante - an ongoing web-based study in France - found a 10% increase in ultra-processed food was linked with a 12% increased risk of cardiovascular disease, 13% increase of coronary heart disease, and 11% for cerebrovascular diseases - which affect the blood supply to the brain and can lead to a stroke.
Ultra-processed foods are distinct and worse for your health than processed foods - common dietary staples such as milk, bacon, simple bread, cheese, tofu and beer.
In comparison, the first study found that diets high in unprocessed and minimally processed foods and lower risks of disease.
Participants in the Seguimiento Universidad de Navarra study were asked to complete a 136-item dietary questionnaire, with foods again grouped according to a degree of processing, with deaths measured over a period of 10 years. For each additional daily serving of ultraprocessed food, mortality risk relatively increased by 18%. Participants who ate more than four servings of processed food per day had a 62% increased risk of all-cause mortality compared to those who ate less than two servings.
Professor Mark Lawrence, nutrition expert at Deakin University in Australia, said research should look at how ultra-processed foods harm different populations around the world.
"Discouraging the consumption of ultra-processed foods; targeting products, taxation, and marketing restrictions on ultra-processed products; and promotion of fresh or minimally processed foods should be considered part of important health policy to improve global public health".
He added policymakers should stop "positioning ultra-processed food as a solution to dietary problems - towards a greater emphasis on promoting the availability, affordability, and accessibility of unprocessed or minimally processed foods".