Fatty ‘ comfort’ foods may make you feel blue, Canadian scientists find
Mice fed high- fat diets show signs of depression and anxiety
Fatty “comfort” foods might make people depressed, new Canadian research suggests.
University of Montreal researchers report that highfat diets increase anxiety and depressive- like behaviours in mice — a finding that a leading Canadian obesity expert said runs counter to almost everything we have been told about fat- dense foods.
High- fat foods are comforting, said the University of Calgary’s Dr. David Lau. Brain scans even show it: they tend to light up different parts of the brain.
That suggests fat- rich foods are so “feel good” they could become addictive and explain why obese people tend to gravitate toward them.
But the authors of the new study found the opposite: mice fed highly palatable, high- fat chow displayed behaviours that were more in keeping, in the animal world, with depression and anxiety.
According to lead researcher Dr. Stephanie Fulton, “fat rich foods can actually cause chemical reactions in the brain in a similar way to illicit drugs, ultimately leading to depression as the “comedowns” take their toll.”
Recent studies increasingly suggest that obesity is linked to a higher risk of depression, said Fulton, but exactly why that might be true — what the underlying biological mechanisms are linking the two — remains obscure. Fulton and her coauthor, Sandeep Sharma, wondered whether a high- fat diet might affect the brain’s emotion and reward circuits.
For their study — which appears in the International Journal of Obesity — the researchers studied a strain of mice prone to obesity. One group was fed a diet high in fat, particularly saturated fat, the other low- fat chow.
After 12 weeks, the animals were put through a series of behavioural tests, including “anxiety” tests measuring how rodents respond to a new environment. Stressed animals tend to freeze, or scurry off to a corner, rather than explore.
Mice exposed to the highfat diet were considerably less active, explored less and avoided open areas.
In a swim test used to measure “behavioural despair”— a test also widely used by drug companies to screen new antidepressants — mice were forced to swim in a glass cylinder filled with water for six minutes.
“Animals that give up quickly — they stop swimming and just float and stop trying to pull themselves out of the beaker — that’s [ a sign of] self- helplessness,” Fulton said.
Mice on the high- fat diet “actually gave up” and attempted fewer escapes, she said.
When the researchers looked at the animals’ brains, they found higher levels of the stress hormone, corticosterone. They also saw changes in the expression of proteins that help control signalling between neurons in areas of the brain regulating emotions and reward.
Fulton said the type of fat might make a difference. Other research has shown that food high in saturated fat — such as hamburgers, bacon, pork sausages, cheese, butter, ice cream — cause inflammation throughout the body, including the brain, and that this inflammation may be causing changes that can lead to “negative mood states.” But Fulton’s lab has found some evidence that animals consuming the same total amount of fat, but “good fat, like olive oil,” experience less anxiety.
The researchers can’t rule out the possibility that the extra fat gained by the mice on the highfat chow affected their performance and “increased immobility times” in the swim test.