Snacking on popcorn, ice cream, or reheated leftovers late at night may cause memory problems when you wake up. Knowing that eating at odd hours could negatively affect the body, researchers from the University of California, Los Angeles (UCLA) School of Medicine, wanted to see what was going on inside the brain. Their findings, published in the journal eLIfe, demonstrate how important a healthy eating routine is to memory.

"We have provided the first evidence that taking regular meals at the wrong time of day has far-reaching effects for learning and memory," said the study's author Dawn Loh, a researcher at the UCLA Laboratory of Circadian and Sleep Medicine, in a press release. "Since many people find themselves working or playing during times when they'd normally be asleep, it is important to know that this could dull some of the functions of the brain."

For the study, Loh and her colleagues regularly fed a group of mice in a six-hour window during the day and studied their ability to remember an object. Next, they restricted food during the day and only fed them in a six-hour window during their normal sleeping hours. When researchers retested their memory after eating late into the night, they found not only did mice struggle more to recall the object, but over a long period of time, they also discovered their long-term memory had dramatically reduced.

Researchers believe the abnormal food schedule impairs the brain's hippocampus — the brain region that manages emotions, the ability to organize, and memory storage. When humans and animals form memories, nerve impulses activate along a specific pathway. After a certain behavior is repeated, that same pathway is reactivated and ultimately reinforced and strengthened. But researchers found activity in the hippocampus to be significantly reduced during midnight eating, indicating that a nightly feeding schedule led to an impaired memory system in mice.

What about genetics? A certain group of genes are in charge of regulating the circadian clock, learning, and memory, which are regulated by a protein called "CREB" (cAMP response element-binding protein). Mice that ate at night also had a significantly less active CREB protein than when they ate during regular eating hours. Because CREB may also play a role in the onset of Alzheimer's, researchers now wonder if unhealthy eating patterns could put a person at greater risk of developing the neurodegenerative disease.

"Modern schedules can lead us to eat around the clock so it is important to understand how the timing of food can impact cogitation," said the study's co-author Christopher Colwell, a psychiatry professor at UCLA, in a press release. "We have shown that simply adjusting the time when food is made available alters the molecular clock in the hippocampus and can alter the cognitive performance of mice."

Source: Colwell CS, Loh DH, Jami SA, et al. Misaligned feeding impairs memories. eLife. 2015.