The More Junk Food You Eat, the Dumber You Get

by Laurent Glatz – for Athletic Carnivore

For several decades, the debate over the impact of industrial food has stirred both scientific and media circles. Beyond obesity, diabetes, or cardiovascular diseases, a more alarming reality is now emerging with clinical consistency: cognitive decline. Intelligence itself, measured by IQ, is decreasing. And the data suggest that the main culprit may be neither school nor screens alone. It’s also the diet.

A series of recent studies converge on a troubling truth: regular consumption of ultra-processed and sugary foods is linked to lower IQ, impaired executive functions, and memory deficits. These findings do not come from isolated or anecdotal trials but from cohorts followed over several years across diverse cultural contexts.

When Junk Food Arrives Early

In China, a 2023 study published in Frontiers in Nutrition tracked 325 children aged 4 to 7 years. The findings are clear: children who regularly consume candy show a drop in overall IQ, with a higher risk of cognitive deficits. Sweet pastries also reduce certain verbal comprehension scores. At this critical age, even a few points difference weigh heavily on brain development.

The British ALSPAC study, conducted on nearly 14,000 children born in the 1990s, is equally revealing. It shows that a diet high in industrial fats and sugars at age 3 correlates with lower IQ at age 8. Even if the diet improves later, the initial harmful effect seems to leave a lasting mark. The brain, like damaged soil, sometimes retains the imprint of its first nourishment.

Even earlier, in utero, effects are measurable. In the United States, Project Viva highlighted an association between high sugar intake during pregnancy and lower cognitive scores in children. A simple daily sugary drink can become more than a harmless habit: it shapes the metabolic environment in which the brain develops.

In Adults, Decline Accelerates

Among adults, the numbers are just as concerning. The Brazilian ELSA study followed over 10,000 adults for 8 years. Those whose diets included a large proportion of ultra-processed foods experienced accelerated cognitive decline, particularly in executive functions: reasoning, planning, and working memory.

The REGARDS study, involving more than 30,000 Americans, showed that increased consumption of ultra-processed foods was linked to a higher risk of cognitive disorders. Conversely, minimally processed foods appear associated with better cognitive protection.

These recent data resonate with a global phenomenon observed over several decades: the Reverse Flynn Effect. Average IQ, which previously rose thanks to better nutrition, education, and health conditions, has started to decline in several developed countries. Norwegian researchers demonstrated that this reversal cannot be explained solely by genetics. Children born to the same families can show different trends from one generation to the next. This historic turning point coincides with the massive rise of the modern agro-food industry.

The Brain Is Not Separate from Metabolism

Biological mechanisms leave little doubt about the plausibility of the link. Ultra-processed foods promote low-grade chronic inflammation, alter gut flora, disrupt the gut-brain axis, and can affect areas like the hippocampus, involved in memory. Oxidative stress generated by these foods can reduce neuroplasticity and weaken learning, concentration, and reasoning abilities.

It’s not just about calories. It’s about signals.

A brain constantly exposed to glycemic spikes, oxidized oils, additives, artificial flavors, and disproportionate reward signals doesn’t just learn to eat differently. It learns to operate amid noise. And a brain functioning amid noise thinks less clearly.

Official consumption data confirm a worrying reality: ultra-processed foods now represent a massive share of energy intake in industrialized countries. These rates spare no social class or generation.

However, it is important to highlight a significant limitation: many studies are observational and thus not conclusive regarding strict causality. But the link is dose-dependent, consistent across continents, and reinforced by current biological knowledge. Critical windows are well identified: early childhood, pregnancy, and middle age appear particularly vulnerable.

Can this trend still be reversed? Yes, probably. But the solution goes beyond simple nutritional advice. It’s a choice of terrain. A choice of stability. A choice of real food.

And if, in this silent battle, junk food were the most insidious weapon: one that doesn’t just fill the body but gradually clouds the mind?