A randomized controlled trial published in the journal Nature Metabolism has found that ultra-processed foods (UPFs) trigger metabolic and neural responses distinct from minimally processed foods—even when the two meals are nutritionally identical. The study provides direct experimental evidence that food processing itself influences health through mechanisms beyond calories and macronutrients alone.
Nutrition Advocacy in Public Interest (NAPi), a group dedicated to addressing UPFs, has written to several Indian ministries and regulatory bodies urging urgent regulatory control over advertising of ultra-processed foods, citing this "growing literature" and what it describes as the failure of self-regulation worldwide, including in India.
Study Finds: Nutritionally Matched, Yet Biologically Different
The study, conducted by researchers at Virginia Tech, involved 57 healthy-weight adults in a randomized crossover design. Participants consumed either a nutritionally matched UPF meal or a non-UPF meal. The meals were matched on weight, energy, energy density, total carbohydrates, fats, proteins, available carbohydrates, glycaemic index, glycaemic load, total dietary fibre, sodium and water—all with less than 1.6% error between meals.
Despite this meticulous matching, the researchers observed significant differences:
Metabolic responses: The UPF meal evoked greater insulinaemic and energetic responses compared with the non-UPF meal. Blood glucose AUC did not differ between conditions, but blood insulin AUC was significantly greater in the UPF condition. Metabolic rate AUC was also greater after the UPF meal. Notably, the respiratory exchange ratio (RER) was higher after the non-UPF meal, indicating differential substrate partitioning. Carbohydrate oxidation was greater following the non-UPF meal, whereas fat oxidation showed the reciprocal pattern—greater in the UPF condition.
The authors note that the pattern of higher insulinemic response with similar peak blood glucose levels is "consistent with a relative reduction in insulin sensitivity," and that the delayed shift in substrate oxidation "is also observed in insulin resistance and type 2 diabetes."
Neural responses: Between-condition differences in peak carbohydrate oxidation were associated with striatal activation in response to food cues. The researchers found that a higher response in the superior temporal gyrus to non-UPF pictures relative to UPF was associated with less carbohydrate oxidation to UPF. Similar associations were observed in the caudate and ventral striatum.
Subjective value vs. neural encoding: Although behavioural measures of subjective food value—measured by willingness to pay in a Becker-DeGroot-Marschak auction task—did not differ between conditions, the neural representation of subjective value did. Brain responses correlated with food valuation were positive for non-UPF but negative for UPF in the visual cortex (fusiform and lingual gyri) and striatum (putamen and caudate).
"Overall, these findings suggest that food processing influences post-ingestive metabolic and neural responses through mechanisms beyond calories and macronutrients alone," the authors conclude.
A Mechanism for Overconsumption?
The researchers propose that altered nutritional availability from changed physical food structure may be a plausible contributor to both overconsumption and metabolic health effects. They note that many UPF products, despite being eaten as solids, are formulated to transition quickly into a lubricated, semi-fluid bolus, facilitating faster and more homogeneous bolus formation. While these manufacturing techniques are intended to optimize oral sensory experience, "they may unintendedly also influence digestion kinetics and downstream metabolic responses."
The study also found that the UPF meal was consumed more slowly than the non-UPF meal—by an average of 1.5 minutes—though the authors consider this difference unlikely to produce a physiologically meaningful effect.
India Context: Rising Consumption, Stalled Regulation
NAPi's letter to Indian authorities points to what it describes as an "extremely rapid rise in consumption of UPFs in India," referencing the Economic Survey 2025-26. Media reports indicate that India's ultra-processed food retail sales surged from US$0.9 billion in 2006 to nearly US$38 billion in 2019—a forty-fold increase. The Economic Survey explicitly identifies obesity and unhealthy diets as economic risks, warning they will drive up healthcare expenditures, reduce labour productivity and impose long-term fiscal burdens.
Despite these warnings, regulatory progress has been slow. India's front-of-pack labelling (FOPL) initiative, launched in 2014, has been stalled for over a decade amid sustained pushback from the food industry. In March 2026, the Supreme Court of India expressed "serious dissatisfaction" with the Food Safety and Standards Authority of India (FSSAI), noting that despite the process being initiated more than ten years ago, "no concrete results" had been achieved. The Court directed FSSAI to prioritise the "right to health" over the "interests of multinational corporations."
Digital Marketing Under Scrutiny
NAPi's letter also cites a recent study published in Appetite, "Contemporary digital marketing techniques used in unhealthy food campaigns targeting young people," which analysed 111 industry reports to document how multinational food and beverage companies are deploying advanced digital marketing techniques—including artificial intelligence, data profiling and personalised targeting—to shape children's food behaviours and influence their diets worldwide. The authors concluded: "Policy actions are needed to protect children from the sophisticated digital marketing techniques used by the food and beverage industry."
Call for Action
NAPi, which describes itself as dedicated to work on UPFs, has offered to engage with the government on the issue. The letter was addressed to the Secretary of the Ministry of Health and Family Welfare, the Secretary of the Ministry of Information and Broadcasting, the Secretary of Consumer Affairs, the Chairperson of the Press Council of India, and the CEO of FSSAI.
Dr Arun Gupta, Founder of BPNI, Convenor of NAPi, and former Member of the Prime Minister's Council on India's Nutrition Challenges, signed the communication.
The study, "Metabolic and neural responses to ultraprocessed foods: a randomized, controlled, crossover study," is authored by Zach Hutelin, Monica Ahrens, Mary Elizabeth Baugh, Emmanuel Nartey, Delbert L. Herald III, Alexandra L. Hanlon and Alexandra G. DiFeliceantonio, and published in Nature Metabolism (2026). It has received 4,894 accesses and an Altmetric score of 384.
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