Consumption of ultra-processed foods contributes to the increase in chronic diseases

What's this about?

People disagree about whether ultra-processed foods cause more long-term health problems. These foods include many snacks, ready meals, and sweet drinks.

What supporters say

• Big studies link high ultra-processed food diets with weight gain, heart disease, some cancers, and earlier death.
• People who ate these foods in one study ate about 500 extra calories each day.
• Those people also gained weight, even when both diets seemed to have similar nutrients.
• These foods may make people eat more because they taste strong, need little chewing, and lack fiber.

What critics say

• Most studies show links, but links cannot prove that these foods alone cause disease.
• People who eat more packaged foods may also have other habits that harm health.
• The best food study had only a small number of people, so we need larger studies.
• Weight gain and extra body fat may explain part of the link with diabetes (a blood sugar illness).

The bottom line

Ultra-processed foods likely raise health risks, mainly because they can lead people to eat more and gain weight. We still cannot say exactly how much harm comes from food processing itself.

Ultra-processed foods — such as many packaged snacks, ready meals and sugary products — are increasingly linked to chronic illness. The evidence suggests that diets heavily based on these foods likely raise health risks, especially by encouraging overeating and weight gain, but it cannot yet say precisely how much harm comes from processing itself.

The case for

Large long-term studies have repeatedly found that people who eat more ultra-processed foods, often called UPFs, have higher rates of obesity, type 2 diabetes, heart disease, some cancers and earlier death. These links have appeared across major European and North American studies, and reviews of the research reach broadly similar conclusions. Individual risks are sometimes modest, but the pattern matters because UPFs are widely consumed and could therefore have a large effect across a population. 1

The strongest experimental evidence comes from a small inpatient feeding trial. Participants ate roughly 500 more calories a day and gained weight when placed on an ultra-processed diet, compared with a minimally processed diet. The meals were broadly matched for the calories, sugar, fat and fiber they were presented as containing, suggesting that the foods’ form and appeal may have led people to eat more. 2

Researchers have several possible explanations. Ultra-processed foods can be highly appealing, easy and quick to eat, calorie-dense, and low in fiber. Their altered texture and structure, along with certain additives or contaminants, may also play a part. But the trial most directly supports one pathway: these diets can increase calorie intake and weight, rather than proving that any particular ingredient or processing feature causes disease. 3

That distinction is important because weight gain and excess body fat probably account for some of the link with diabetes and other illnesses. In studies of diabetes, the apparent effect of UPFs often becomes smaller after researchers account for body weight and lifestyle. This is consistent with the idea that greater intake and weight gain are major routes through which UPFs affect health, though it does not rule out additional effects.

The case against

The main weakness is that most evidence tying UPFs to diabetes, heart disease, cancer and death comes from observational studies. Such research can show that two things move together, but it cannot fully separate the effects of food from income, education, exercise, smoking, wider diet quality and other differences in people’s lives. That leaves uncertainty over whether UPFs themselves cause the full level of risk observed. 5

Measuring exposure is also difficult. Many studies depend on food questionnaires or dietary recalls, while products and recipes change over time. Researchers must also classify foods using the NOVA system, and that coding can differ between countries. These problems can misjudge how much ultra-processed food people actually eat and make studies harder to compare. 7

Critics also argue that the UPF label groups together foods that may have very different nutritional qualities and roles in a diet. It should not be treated as though every item in the category has the same biological effect (see Figure 1). The evidence is more consistent with risk varying among different kinds of UPFs than with a finding that all ultra-processed foods are equally harmful. 6

The controlled trial, while important, has limits too. It was small, short and conducted in an inpatient setting. It measured short-term eating and weight change, not new cases of diabetes, cardiovascular disease, cancer or death. It therefore strengthens the case for a causal pathway through overeating and weight gain, but cannot alone establish long-term disease causation. 8

The bottom line

The overall evidence indicates that diets high in ultra-processed foods likely make a meaningful contribution to chronic-disease risk, particularly because they can drive higher calorie intake, weight gain and obesity. The association is a substantial public-health concern, given how common these foods are. 4

But the evidence does not show that every ultra-processed food independently causes disease, or provide a precise estimate of the risk caused by processing as a whole. The clearest practical conclusion is to limit dietary patterns dominated by energy-dense, highly appealing UPFs — especially when they replace minimally processed foods — rather than assume that occasional consumption of every food in the category carries the same harm.