Junk Food, Shrinking Brains: New Research Links Processed Diets to Structural Changes in Toddlers' Brains

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A Six-Year Study, One Consistent Pattern

Researchers at Children's Hospital Los Angeles followed 144 mostly Latino and Hispanic mother-infant pairs from birth through age 6. At four points in early childhood — 6, 12, 24, and 72 months — they recorded how much of each child's diet came from ultra-processed foods (UPF) using repeated 24-hour dietary interviews with parents.

At age 6, the children underwent MRI brain scans. The result, published in The American Journal of Clinical Nutrition, was striking: every 10 percent increase in cumulative UPF intake was linked to a nearly 2 percent decrease in the volume of several subcortical brain structures — including the accumbens, amygdala, pallidum, putamen, and thalamus.

These regions sit deep beneath the brain's outer layer (the cortex) and are central to processing reward, emotion, and motivation.

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No Change in Test Scores — Yet

One detail surprised the research team: despite the structural differences, the study found no link between ultra-processed food consumption and children's performance on cognitive tests. Memory, language, attention, and processing speed all scored within normal ranges.

Lead author Jonatan Ottino-González and senior author Michael I. Goran, director of the Nutrition and Obesity Program at the hospital's Saban Research Institute, say that gap is itself worth attention. Structural brain changes may show up years before any measurable effect on behavior or learning — meaning problems could be building quietly, long before a teacher or parent would notice anything wrong.

"Our findings suggest that what children eat early in life may shape brain development in ways we're just beginning to understand," Goran said, adding that even without differences in cognitive performance, the team observed measurable changes in brain structure.

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Why Early Childhood Matters So Much

The first years of life are considered a uniquely sensitive window for brain development, marked by high neuroplasticity — the brain's ability to reorganize its neural connections. Diet quality during this period has previously been linked to neurodevelopment more broadly, and earlier studies in adults have already tied high UPF consumption to lower brain volume and cognitive problems, including impaired attention, working memory, and even dementia risk.

The Los Angeles study is one of the first to apply that same question to very young children using brain imaging — a population that has received far less research attention than adults.

Because the study is observational, it cannot prove that ultra-processed food directly causes the brain changes. The researchers are careful to describe it as an association, not proof of cause and effect. Goran said the team's next goal is identifying which developmental windows are most sensitive and which biological mechanisms — inflammation, nutrient deficiencies, or something else entirely — might be driving the pattern.

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The Scale of the Problem

The findings land against a troubling backdrop. In the United States, ultra-processed foods now make up roughly 73 percent of the entire food supply, and by some estimates nearly 70 percent of children's daily calories come from these products. Health officials have already flagged the trend as a driver of the country's childhood obesity and chronic-disease crisis.

That concern has now reached the federal government. Health and Human Services Secretary Robert F. Kennedy Jr., appointed under President Donald Trump, has made ultra-processed foods a central target of the administration's MAHA agenda. In August 2026, HHS announced it was finalizing the federal government's first official definition of "ultra-processed food," alongside reforms to how food additives are approved. "Nearly 60% of the American diet is made up of ultra-processed foods, and childhood obesity now affects more than one in five American children," Kennedy said, calling the reforms a step toward transforming the food system.

Whether such federal action will meaningfully reduce children's exposure to these products remains an open question — earlier MAHA reports were criticized for stopping short of concrete restrictions on UPF sales. But the new brain-imaging findings from Los Angeles give the debate added scientific weight, at a moment when Washington is, for the first time, moving to formally define and regulate the category.

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Practical Advice for Parents

Nutrition experts say families don't need to aim for perfection — small, consistent shifts matter more than eliminating processed food entirely.

Cook more at home, using whole ingredients such as vegetables, fruit, grains, and protein rather than pre-packaged meals.

Shop the perimeter of the grocery store, where fresh, less-processed foods are typically located, and check ingredient labels for short lists of recognizable items.

Watch for red flags, including high-fructose corn syrup, partially hydrogenated oils, and artificial colors or flavors.

Prepare healthy snacks in advance — sliced apples with peanut butter, hard-boiled eggs, plain yogurt with berries, or vegetables with hummus.

Make water the default drink, limiting sugary beverages to occasional treats.

As one dietitian not involved in the study put it: most children will eat some processed food, and that's fine. What matters most is the overall pattern — a diet built mainly around whole foods, with room left over for pizza night and birthday cake.

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Outlook

The Los Angeles team plans further research to pin down exactly how and when ultra-processed diets affect the developing brain. Combined with Washington's new push to formally regulate the category, the coming years could bring both clearer science and, potentially, real policy change — a rare alignment between research findings and political will that advocates have been pushing for since the first MAHA report was released.

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Sources

1. Children's Hospital Los Angeles (press release): https://www.chla.org/blog/experts/research-and-breakthroughs/ultra-processed-foods-linked-brain-differences-young-children
2. Psychiatry Advisor: https://www.psychiatryadvisor.com/news/consumption-of-ultraprocessed-foods-in-early-childhood-linked-to-brain-development/
3. Medical Xpress: https://medicalxpress.com/news/2026-07-ultra-foods-linked-brain-differences.html
4. U.S. Department of Health and Human Services (HHS.gov): https://www.hhs.gov/press-room/hhs-announces-ultra-processed-foods-gras-reforms.html
5. Harvard T.H. Chan School of Public Health (context on MAHA/UPF policy debate): https://hsph.harvard.edu/news/will-rfk-jr-really-curb-ultra-processed-foods-like-he-promised-experts-weigh-in

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