Fructose changes brain to cause overeating, scientists sayFructose, a common sugar found in the U.S. diet, may cause changes in the brain that trigger a person to overeat, a new brain imaging study shows.After drinking a fructose beverage, the brain doesn't register the same feeling of being full as it does when simple glucose is consumed, scientists found.All sugars are not equal -- even though they contain the same amount of calories -- because they are metabolized differently in the body. Table sugar is sucrose, which consists of half fructose, half glucose. High-fructose corn syrup is 55 percent fructose and 45 percent glucose. Some nutrition experts say this sweetener may pose special risks, but others and the industry reject that claim. And doctors say we eat too much sugar in all forms.For the small study, published Jan. 2 in the Journal of the American Medical Association (JAMA), scientists used magnetic resonance imaging, or MRI, scans to track blood flow in the brain in 20 young, normal-weight people before and after they had drinks containing glucose or fructose in two sessions spaced several weeks apart.The brain scans showed that drinking glucose "turns off or suppresses the activity of areas of the brain that are critical for reward and desire for food," said one study leader, Dr. Robert Sherwin, chief of endocrinology at Yale University School of Medicine in New Haven, Conn.With fructose, "we don't see those changes," he said. "As a result, the desire to eat continues -- it isn't turned off."The researchers saw these changes in the hypothalamus, insula, and striatum, which are regions of the brain that regulate appetite, motivation, and reward processing, in addition to increasing connections in certain brain pathways linked to satiety....http://www.cbsnews.com/8301-204_162-57561593/fructose-change...January 2, 2013 Effects of Fructose vs Glucose on Regional Cerebral Blood Flow in Brain Regions Involved With Appetite and Reward PathwaysJAMA. 2013;309(1):63-70. doi:10.1001/jama.2012.116975.Importance Increases in fructose consumption have paralleled the increasing prevalence of obesity, and high-fructose diets are thought to promote weight gain and insulin resistance. Fructose ingestion produces smaller increases in circulating satiety hormones compared with glucose ingestion, and central administration of fructose provokes feeding in rodents, whereas centrally administered glucose promotes satiety.Objective To study neurophysiological factors that might underlie associations between fructose consumption and weight gain.Design, Setting, and Participants Twenty healthy adult volunteers underwent 2 magnetic resonance imaging sessions at Yale University in conjunction with fructose or glucose drink ingestion in a blinded, random-order, crossover design.Main Outcome Measures Relative changes in hypothalamic regional cerebral blood flow (CBF) after glucose or fructose ingestion. Secondary outcomes included whole-brain analyses to explore regional CBF changes, functional connectivity analysis to investigate correlations between the hypothalamus and other brain region responses, and hormone responses to fructose and glucose ingestion.Results There was a significantly greater reduction in hypothalamic CBF after glucose vs fructose ingestion (-5.45 vs 2.84 mL/g per minute, respectively; mean difference, 8.3 mL/g per minute [95% CI of mean difference, 1.87-14.70]; P = .01). Glucose ingestion (compared with baseline) increased functional connectivity between the hypothalamus and the thalamus and striatum. Fructose increased connectivity between the hypothalamus and thalamus but not the striatum. Regional CBF within the hypothalamus, thalamus, insula, anterior cingulate, and striatum (appetite and reward regions) was reduced after glucose ingestion compared with baseline (P < .05 significance threshold, family-wise error [FWE] whole-brain corrected). In contrast, fructose reduced regional CBF in the thalamus, hippocampus, posterior cingulate cortex, fusiform, and visual cortex (P < .05 significance threshold, FWE whole-brain corrected). In whole-brain voxel-level analyses, there were no significant differences between direct comparisons of fructose vs glucose sessions following correction for multiple comparisons. Fructose vs glucose ingestion resulted in lower peak levels of serum glucose (mean difference, 41.0 mg/dL [95% CI, 27.7-54.5]; P < .001), insulin (mean difference, 49.6 µU/mL [95% CI, 38.2-61.1]; P < .001), and glucagon-like polypeptide 1 (mean difference, 2.1 pmol/L [95% CI, 0.9-3.2]; P = .01).Conclusion and Relevance In a series of exploratory analyses, consumption of fructose compared with glucose resulted in a distinct pattern of regional CBF and a smaller increase in systemic glucose, insulin, and glucagon-like polypeptide 1 levels.http://jama.jamanetwork.com/article.aspx?articleid=1555133
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