Stephanie Fulton

“High-fat feeding can cause impairments in the functioning of the mesolimbic dopamine system,” says Stephanie Fulton of the University of Montreal and the CHUM Research Centre (CRCHUM). This system is a critical brain pathway controlling motivation.

Fulton’s research, published in Neuropsychopharmacology, may have great significance. “Our research shows that independent of weight gain and obesity, high-fat feeding can cause impairments in the functioning of the brain circuitry profoundly implicated in mood disorders, drug addiction, and overeating – several states and pathologies that impinge on motivation and hedonia,” Fulton explained. Hedonia relates to a mental state of wellbeing. “Another key finding is that the effects of prolonged high-fat feeding to dampen the sensitivity of this brain reward system are specific to saturated fats – palm oil used in this study – but not monounsaturated fat such as the olive oil used in this study.”

Ricoh Company Ltd.
Ricoh Company Ltd.

Researchers derived these findings by working with three groups of rats. The first group of rats was the control group: these rats were given a low fat diet containing equal amounts of monounsaturated and saturated fatty acids. The second group of rats was given a monounsaturated high fat diet, of which 50% of the calories were from fat derived  from oil. The third group was given a saturated high fat diet of which 50% of the calories were from fat, but this time the fat was derived from palm oil. The high fat diets were equal in terms of sugars, proteins, fat content, and caloric density; the amount eaten by the rats was not controlled. At the end of the eight weeks, all of the rats had comparable body weights and levels of insulin, leptin (a major metabolic hormone) and glycemia.

Fat-People-Eating-Pictures-14-570x499During this time, the rats underwent a series of behavioral and biochemical tests known to be indicators of the functioning of the rats’ dopamine system. “We established that the rats on the palm diet had a significantly blunted dopamine function,” said Cecile Hryhorczuk, the first author of the study. “Our research group and others hypothesize that this leads the brain to try to compensate by heightening reward-seeking behavior, much like the phenomenon of drug tolerance where one has to increase the drug dose over time to get the same high. So, a person consuming too much saturated fat may then compensate a reduced reward experience by seeking out and consuming more high-fat and high-sugar foods to get the same level of pleasure or reward.”

Fulton et al.’s research is a first of its kind to point out, regardless of weight changes, unrestricted intake of saturated fats can have negative effects on the controls of motivation by the brain. “As we were able to control for changes in body weight, hormones, and glucose levels, we think that the fats may be affecting the dopamine system by a direct action in the brain,” Fulton said. “We in fact have separate evidence that brain inflammation could be involved in this process, as it is evoked by saturated high-fat feeding, which will be presented in a future publication.”

About this study:

Stephanie Fulton and her colleagues published, “Dampened mesolimbic dopamine function and signaling by saturated but not monounsaturated dietary lipids” in Neuropsychopharmacology on July 14, 2015. Stephanie Fulton, PhD, is a professor at the University of Montreal’s Department of Nutrition while Cecile Hryhorczuk, MSc, is affiliated with the university’s Department of Physiology. Both are researchers at the Montreal Diabetes Centre and the CHUM Research Centre (CRCHUM.)

This research was supported by funding from the Canadian Institutes for Health Research (MOP123280, MOP115042, MOP9575), the Fonds de Recherché Quebec-Santé, the National Science and Engineering Research Council (249848-2007 RGPIN), the Montreal Diabetes Research Center/Université de Montréal and CMDO/Novo Nordisk.

The University of Montreal is officially known as Université de Montréal.

University of Montreal

MNT. (2015, JULY 15). Retrieved from THIS IS YOUR BRAIN ON FRIED EGGS:

Raillant-Clark, W. (2015, July 14). THIS IS YOUR BRAIN ON FRIED EGGS. Retrieved July 19, 2015, from CRCHUM:

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