Our Brains Like Sugar More Than FatTuesday, December 3, 2013
Fat, sugar and salt are often put up as the holy trinity of unhealthy eating. Together, foods considered high in one or more of these substances are generally considered “highly palatable” – a fancy way of saying they taste good.
However, biochemically, biologically, physiologically, and otherwise, these substances are vastly different (NaCl or salt being the most simple of the three).
Now, based on a fascinating neuroimaging study by Eric Stice and colleagues, from the Oregon Research Institute, published in the American Journal of Clinical Nutrition, suggests that sugar and fat act very differently on the reward areas of the brain (salt was not studied).
Highly sophisticated functional magnetic resonance studies were conducted in 106 non-obese adolescents who were given equicaloric amounts of high-fat/high-sugar, high-fat/low-sugar, low-fat/high-sugar, and low-fat/low-sugar chocolate milkshakes with a tasteless solution acting as control.
While high-fat shakes resulted in greater activation in brain regions involved in associative learning processes (caudate and hippocampus) and somatosensory regions (postcentral gyrus), the high-sugar shekes prompted greater activation in regions associated with reward and motivation (insula and putamen), oral somatosensation (Rolandic operculum), and gustatory stimulation (thalamus).
While increasing sugar in low-fat milkshakes caused greater activation in the bilateral insula and Rolandic operculum, increasing fat content did not elicit greater activation in any region.
The authors offer the following explanation for these interesting findings:
“It is possible that this pattern of findings emerged because sweet is a primary reward, and it has been subsequently theorized that humans are predisposed with a sweet preference, whereas fat is viewed as a texture, and preferences are acquired through conditioning at an early age.
It is also conceivable that gustatory regions that encode tastes project more directly to reward-valuation regions than oral somatosensory regions that encode viscosity and, therefore, the fat content of foods. Collectively, results from the current study supported the notion that increasing the sugar content of food results in a greater neural response than increasing the fat content.”
From a practical perspective, this study clearly implies that while it may be easy to make low-fat foods more palatable and rewarding by simply adding sugar (something that we know happened as a result of the “low-fat” diet craze), it is far less likely that adding fat to low-sugar foods (and beverages) would do the same.
Thus, the authors suggest that,
“…policy, prevention, and treatment interventions should prioritize reductions in sugar intake.”
Given the direct stimulatory effect of sugar on reward centres, I can only wonder how cutting sugar will affect reward seeking behaviours, which makes me wonder if any of my readers have ever experienced increased cravings for other “stimulants” when they have tried to cut down on sweets.
Hat tip to Danielle Aldous for alerting me to this paper.
Stice E, Burger KS, & Yokum S (2013). Relative ability of fat and sugar tastes to activate reward, gustatory, and somatosensory regions. The American journal of clinical nutrition, 98 (6), 1377-84 PMID: 24132980