Sugary Diets May Cause Long-Term Memory Problems Even after Eating Improves
An analysis of 27 animal studies found that switching to a healthier diet improved memory performance, although the effects were much weaker after a high-sugar diet.
Rehn and others. performed a systematic review and meta-analysis of the cognitive and behavioral effects of diet reversal in rodent models. Image credit: Steve Buissinne.
“Our results show that improving diet quality is beneficial for memory,” said Dr Simone Rehn, a researcher at the University of Technology Sydney.
“But these improvements were incomplete. Even after weeks of eating a healthy diet, memory did not return to the level seen in animals that had never been on an unhealthy diet.”
Dr. Rehn and colleagues conducted a systematic review and meta-analysis of 27 preclinical studies to identify consistent trends across experiments.
They focused on memory, but also looked at anxiety- and depression-like behaviors, general activity, and motivation for food.
In all studies, animals that adopted a healthy diet performed better on memory tasks than those that continued to eat unhealthy foods.
However, memory recovery depended on diet composition, with recovery observed in experiments using high-fat diets, but not in those using high-sugar diets or diets combining high fat and sugar.
No consistent improvements were seen in anxiety, activity levels or eating motivation, suggesting that the effects were specific to memory rather than general behavior.
“We saw clearer improvements in memory after replacing high-fat diets with healthy foods,” Dr. Rehn said.
“But diets high in added sugars, including diets high in fat and sugar, have shown little evidence of recovery.”
“This suggests that sugar may be a key factor in limiting memory retrieval.”
The memory tasks analyzed reflect the function of the hippocampus, a brain region essential for learning and memory, and also involved in the regulation of appetite and food intake.
“Animal models have been key to understanding how diet affects the brain,” said Dr Mike Kendig, also from the University of Technology Sydney.
“In humans, changes in diet typically occur alongside changes in exercise, mood, and daily routine, making it very difficult to separate the effects of diet alone on brain function.”
“There is a widespread belief that the effects of a poor diet are easily reversible. »
“These results suggest that, at least for the record, the situation might be more complicated, particularly when diets are high in added sugars.”
“Improving diet quality is always worth it. But protecting brain health may also depend on avoiding prolonged exposure to an unhealthy diet, rather than assuming that the effects can always be completely reversed later.”
The review article was published on May 17, 2026 in the journal Nutritional neuroscience.
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Simone Rehn and others. Cognitive and behavioral effects of reversing a high-fat, high-sugar diet: a systematic review and meta-analysis of animal studies. Nutritional neurosciencepublished online May 17, 2026; doi: 10.1080/1028415X.2026.2664635
