Ultra-processed foods (UPFs) may change how children’s brains respond to food cues, potentially helping explain the link between their consumption and weight gain, according to a new study published in JAMA Network Open. The findings come amid renewed calls from nutrition advocates for the government to restrict advertising of unhealthy foods to children.

Researchers from the University of Southern California and Kaiser Permanente studied 46 children with healthy weight, with an average age of 8.7 years. Using functional magnetic resonance imaging (fMRI), they examined how the children’s brains responded to food-related images and tracked changes in their body composition over the following year.

The study found that children who habitually consumed more UPFs showed stronger responses to food cues in the dorsal striatum, a brain region involved in learning, reward-related behaviour and habit formation. Greater responsiveness in this region was, in turn, associated with increases in body mass index (BMI) and body fat percentage over one year.

The findings suggest that reward-related brain responses could be one pathway linking UPF consumption with increasing body fat during childhood. However, the researchers cautioned that the observational study cannot establish that UPFs directly cause these brain responses or subsequent weight gain.

How food cues may influence eating habits

Researchers found that repeated exposure to highly palatable foods may reinforce responses to food-related cues, making eating behaviour increasingly habitual.

The researchers found that higher habitual UPF consumption was associated with greater dorsal striatal activation when children were shown food cues. These children experienced greater increases in BMI and body fat percentage over the subsequent year.

When the researchers accounted for dorsal striatal responsiveness in their statistical models, the association between UPF intake and changes in BMI was reduced by 31%, while the association with body fat percentage was reduced by 44%. This suggests that brain responses may help explain part of the relationship between UPF consumption and increasing adiposity.

The study also found an association between higher UPF intake and an increase in waist circumference over one year.

The authors noted that added sugar alone was unlikely to explain the observed relationship. Experimental research suggests that combinations of fat and carbohydrates, which are characteristic of many highly palatable processed foods, can produce stronger striatal reward signalling than either nutrient alone.

To their knowledge, the researchers said, this was the first study to provide evidence that dorsal striatal responses to food cues may represent a neural pathway linking habitual UPF intake with subsequent increases in adiposity in children.

However, the study included only 46 children, and the researchers stressed that larger studies are needed to confirm the findings. They also noted that children with an inherently stronger response to food cues might be more likely to consume UPFs, rather than the foods necessarily producing the differences in brain activity.

The findings therefore point to a possible mechanism, rather than establishing that UPFs are addictive or that they directly alter children’s brains.

NAPi calls for restrictions on junk-food advertising

For Dr Arun Gupta, convenor of the Nutrition Advocacy in Public Interest (NAPi) network and a co-author of The Lancet series on ultra-processed foods published in 2025, the findings reinforce concerns about the commercial promotion of unhealthy foods to children.

“This study moves the debate from obesity to addiction,” Gupta said.

He argued that food marketing and the design of highly palatable products should be considered alongside individual and parental choices when addressing childhood obesity.

Gupta also raised concerns about advertisements featuring cartoon characters, celebrity endorsements, promotional offers such as ‘Buy 1 Get 1’, and health claims that may influence children’s perceptions of packaged foods.

The study itself did not investigate advertising or measure the effects of marketing on children’s eating behaviour. However, its findings add to the wider debate about how repeated exposure to highly palatable foods and food-related cues may influence eating habits.

A policy proposal awaiting a response

NAPi has been pressing for restrictions on the advertising of foods high in fat, sugar and salt (HFSS), arguing that measures focused only on consumer awareness place too much responsibility on families.

India’s National Multi-Sectoral Action Plan for Prevention and Control of Common Non-Communicable Diseases (2017–2022) called for the prohibition of advertising HFSS food products. NAPi has also sought amendments to the Press Council of India’s Norms of Journalistic Conduct 2022 to include HFSS foods among products whose advertising should be prohibited.

In May 2024, according to NAPi, the Press Council said the proposed amendment did not fall within its remit and directed the organisation to the Ministry of Health and Family Welfare (MoHFW). In June 2025, the Press Council sought specific comments from the Health Ministry on the proposal. NAPi says a response was still awaited in 2026, despite a reminder from the Press Council.

The organisation has also written to the Ministry of Information and Broadcasting seeking changes to advertising rules.

The proposal seeks to extend restrictions beyond traditional tobacco and alcohol advertising to the promotion of HFSS foods. Such a change would require appropriate regulatory action; the existing policy plan and NAPi’s submissions do not, by themselves, establish that a comprehensive ban is currently in force or that the Health Ministry has formally rejected the proposal.

The question is particularly relevant as India grapples with rising rates of obesity and other diet-related non-communicable diseases. The Indian Council of Medical Research’s dietary guidelines have highlighted the contribution of unhealthy diets to the country’s disease burden. The Economic Survey 2024–25 also discussed the public-health concerns associated with ultra-processed foods.

Why the distinction matters

UPFs are not a single category of food defined simply by high sugar or fat content. Under the NOVA classification system used by the researchers, the category includes industrially formulated products that often contain ingredients and additives not commonly used in home cooking. Not all processed foods are necessarily ultra-processed, and nutritional quality varies between products.

The new study adds a potential brain-related explanation to evidence linking high UPF consumption with adverse health outcomes. But it does not establish that every UPF has the same effect, nor does it prove that children who eat these foods will develop obesity.

For policymakers, the findings raise a broader question: should measures to protect children’s diets rely primarily on educating parents and encouraging individual choice, or should they also address the commercial environment in which children encounter food?

NAPi argues that stronger restrictions on the promotion of unhealthy products are needed. The research does not itself prescribe a particular advertising policy, but it adds to the evidence that childhood food consumption and weight gain may involve more than a simple calculation of calories.

For now, the study offers a warning and a research lead: the relationship between what children eat, how they respond to food cues and how their bodies change over time deserves closer scrutiny. Whether this evidence translates into stronger regulation will depend on further research and government action.