Blood glucose levels control the desire for high-calorie foods through brain activation
High-calorie foods are widely spread in our society and a fierce enemy in the fight against obesity. A study conducted by researchers at Yale University and the University of Southern California has shown that normal blood glucose levels control the urge for high-calorie foods and this appetite suppressing effect might be lost in obese individuals.
Circulating glucose is the primary fuel source for the brain. It is known that a mild decrease in circulating glucose causes hunger. This study also looked into the effect of normal circulating glucose on certain brain regions and its subsequent influence on high-calorie food intake. The use of brain imaging (fMRI) allowed them to investigate the brain of 14 healthy (5 obese and 9 non-obese) participants. Seven individuals were used as a control. Brain imaging was combined with a stepped hyperinsulinemic euglycemic-hypoglycemic clamp (a technique to control blood glucose levels) after a standardized meal, consumed 2 hours in advance. The desire for high-calorie foods after changes in circulating glucose was measured by the use of different food and non-food images.
They found that a slight reduction in blood glucose levels to 67 ± 1 mg/dl, activates limbic-striatal brain regions (image = blue parts) and this increases the desire for high-calorie foods. However, normal circulating glucose levels (88 ± 2 mg/dl) trigger the medial prefrontal cortex (image = red and yellow parts), an area of the brain known to regulate emotions and impulses, causing a reduced interest in food. Interestingly, this later effect was lacking in obese individuals (see image).
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This study has shown that blood glucose levels are able to reduce or increase our desire for high-calorie foods by affecting different regions in the brain. Foods packed with sugar and other high glycemic carbohydrates spike the secretion of insulin, which is followed by drops in circulating glucose stimulating the desire for high-calorie foods. Sadly enough these foods are omnipresent in our fast food society. Keeping circulating glucose constant appears to be a good strategy to reduce high-calorie food intake, at least in lean individuals. This can be achieved by the use of regular and smaller meals. Another option is the use of complex carbohydrates over their refined counterparts. This study also indicates that there might be a biological difference in appetite suppression between lean and obese individuals, causing more difficulties for obese people to control their desire for high-calorie foods.
Excerpt image by celebrity-diets.org
Page, K. A., Seo, D., Belfort-DeAguiar, R., Lacadie, C., Dzuira, J., Naik, S., et al. (2011). Circulating glucose levels modulate neural control of desire for high-calorie foods in humans. Journal of Clinical Investigation, 121(10), 4161-4169.