Western-style diet may impair memory, affect appetite control

Previous research has shown that animals fed a Western-style diet (WS-diet), rich in saturated fat and added sugar, suffer from impaired hippocampal function, which not only affects memory but can also regulate appetite. A study published in Royal Society Open Science suggests that humans respond similarly.

The researchers enlisted 110 healthy, lean adults and randomly assigned them to either a one-week WS-diet intervention or a habitual-diet control group. They obtained measures of hippocampal-dependent learning and memory (HDLM) and appetitive control before and after the intervention. Additionally, the researchers retested for HDLM at the three-week follow-up.

One week’s exposure to a WS-diet caused a measurable weakening of appetitive control, as measured by the two key ratings on the wanting and liking test. Before the intervention, participants viewed palatable breakfast foods and judged how much they wanted to eat them, and then how much they liked their actual taste. This test was repeated after participants had eaten to satiety. Across the pre- and post-meal tests, wanting ratings declined far more than ratings of taste liking. This manifestation of appetitive control—that is the expectation that food is less desirable than it actually tastes—changed in participants following the Western-style dietary intervention. When sated, the WS-diet group reported an equivalent decline in wanting and taste liking.

The researchers also found that relative to controls, HDLM performance declined in the WS-diet group, but was not different at follow-up. The observed decline in HDLM strongly correlated with the change in appetitive control measured by the wanting and liking test, suggesting a probable common hippocampal basis for this effect.

“More broadly, this experiment, alongside those from the other animal and human studies cited here, suggests that a WS-diet causes neurocognitive impairments following short-term exposure,” concluded the researchers.

Study