New York: Chips, sodas and frozen pizzas tend to be full of salt, sugar and fat, but now scientists are trying to understand if there is anything else about such processed foods that can be bad for us.  The spread of cheap, packaged foods has already been linked to rising obesity around the world. But advice for limiting processed foods may seem unhelpful, considering how convenient they are and the growing range of products that fall into the category.
While three recent studies offer more clues on how our increasingly industrialized food supply can affect our health, they also emphasize how difficult nutritional and counseling can be. Here's what they say.
What does "processed" mean?
If it cures, freezes, cuts or pasteurises, almost all foods undergo some type of processing. Although the processing itself does not automatically make food unhealthy, "processed foods" are generally a negative term.
To clarify the most processed food products, researchers came to a system that groups foodstuffs into four categories. It is far from perfect, but the system says that highly processed foods are mostly made from industrialized ingredients and additives, with little or no intact whole foods.
Sodas, packaged cakes, instant noodles and chicken nuggets are some examples of highly processed foods. But also included are products that may seem healthy, such as breakfast cereals, energy bars and some yogurt.
What is wrong with processed foods?
Cheap packaged foods are everywhere including checkout lines, gas stations and vending machines and a very small four-week clinical study can deepen our understanding of why it is likely to moisturize obesity.
Researchers at the National Institute of Health found that people ate an average of 500 extra calories a day when fed mostly processed foods, as compared to when the same people were fed minimally processed foods. It was even though researchers tried to match the meals for nutrients such as fat, fiber and sugar.
The 20 participants had to eat as much or as little as they wanted and were controlled to a clinic so that their health and behavior could be monitored. It's not all the bad news.
In another study based on questionnaires, researchers in France found people who ate more processed foods more likely to have heart disease. A similar study in Spain found that eating more processed foods was linked to a higher risk of death in general.
What is it about processed foods?
In addition to the fact that they taste really good, it may happen that Other reasons why it is so difficult to stop eating food like cheesecake and ice cream.
When feeding minimally processed foods, people in clinical trials produced more of a hormone that suppresses appetite and less of a hormone that causes hunger. The reason for the biological reaction is not clear. Another discovery: People at processed foods faster.
"These foods tend to be softer and easier to chew and swallow," said Kevin Hall, a researcher at the National Institutes of Health who led the study.
Hall noted Source of nutrients can make a difference. For example, whole fruit and vegetable fiber may be better for making people feel full of the types of fiber added to packaged foods such as cakes, yogurt and even soft drinks.
For the French study, author Mathilde Touvier also noted largely unexamined effects of "cocktail" of additives used to make the various processed foods we eat.
All three studies come with great approaches. The American survey was small and individual behavior varied widely: Some ate about the same amount of calories on both diets and others ate much more at the processed diet.
The meals in the two diets were judged to be as nice, but Hall noted it was possible participants said what they thought they should. The processed food diet included foods such as salted nuts and whole milk compared to unsalted nuts and lean milk for unprocessed diet.
With French and Spanish studies, there may be other habits and environmental factors that explain the differences in health risks. The studies also did not reflect the wider population. In the Spanish study, the participants were college graduates and relatively younger. And even though processed food was associated with a greater risk of death, the total number of deaths was still relatively small.
What should you eat?
Even without the latest studies, it was advised that limiting processed foods probably gives meaning to most people. Minimal processed foods tend to be richer in nutrients and more difficult to eat, as they are not so widely available and practical. It is still difficult to follow this advice, especially if it is for people with limited time and money to spend on food.
"What frustrates me is when the message is" Change how you eat "but think about why people eat how they eat," says Sarah Bowen, a professor studying food and inequality at North Carolina State University.
Another challenge is the broad spectrum of processed foods and to distinguish which ones may be better or worse when companies are constantly regenerating products to make them appear healthier. So while the newest studies can give us more reasons to avoid industrialized foods, they also underline the difficulty of providing solutions.