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A new study finds that fructose consumption has distinct effects on brain regions that regulate appetite, a possible mechanism for ‘ever-eating’ and the widespread rise in obesity and other related disorders.
The study, led by Dr Robert Sherwin at Yale University in the US, used magnetic resonance imaging (MRI) techniques to look at the activity of brain regions associated with appetite and reward systems, to assess how they respond to fructose versus glucose. Dramatic increase in fructose consumption correlated with obesity & diabetes
Increases in fructose consumption have risen dramatically since the creation of high fructose corn syrup (HFCS). HFCS has largely replaced table sugar as the most common industrial sweetener, especially in the US where most processed foods including soft drinks contain high levels of the sugar substitute. Industrial-scale, cheap over-production of corn since the Nixon era in the early 1970s laid the foundations for the wide-spread use of HFCS, and this continues today with the US devoting roughly a quarter of its agricultural land to corn crops, the majority of which are now genetically modified (GM).
Rise in HFCS consumption over the last few decades appear to correlate with the sharp increase in obesity and other diet-related disorders including diabetes, suggesting fructose as a major contributory factor. The HFCS used in beverages is usually 55 % fructose and 41 % glucose (HFCS55). Since its introduction, higher quantities of HFCS than sucrose is added despite it being sweeter (sucrose is a disaccharide of both fructose and glucose). The excessive consumption of fructose is therefore considered a major health risk.
Brains respond differently to fructose
In the new study, 10 people consumed fructose or glucose drinks 15 minutes before their brains were analyzed for cerebral blood flow, an indirect measure of brain activity. They then mapped out the regions of the brain with significantly reduced blood flow; very different patterns emerged with the two sugars (Figure 1).
Figure 1 Reduced cerebral blood flow (marked in blue) after glucose (upper panel) and fructose ingestion at different sections of the brain on fMRI
Glucose lowered cerebral blood flow in the hypothalamus, a region that controls appetite and fuel sensing and regulates hunger, among other metabolic processes including thirst, and circadian rhythm. Glucose also reduced activity in other brain regions that are thought to act in synchrony to read a person’s metabolic state and drive motivation and reward – the thalamus, insula, anterior cingulate and striatum.