Ingesting fructose could be making you hungry, concludes a study by Robert Sherwin, M.D., and colleagues at Yale University published in the Journal of the American Medical Association in January. Employing functional MRIs (fMRIs), researchers looked at the differences in cerebral blood flow produced by fructose and glucose drinks in 20 healthy non-overweight volunteers. Study participants rated their perception of hunger before and after drinking the sweetened beverages.
Unlike glucose, which potently stimulates insulin release, fructose is known to be a weak activator of insulin and dampens the response of glucagon-like peptide (GLP-1), a hormone known to maintain insulin levels. Both of these conditions can lead to increased hunger signals and higher glucose levels in the blood.
The fMRIs showed that glucose-sweetened drinks reduced blood flow in the regions of the brain affecting a person’s feelings of satiety, while fructose produced less of a decline in blood flow in some of the same regions. In these satiety regions, reduced blood flow signals to the body a feeling of fullness, regulating food intake.
The participants’ ratings of their satiety level correlated with the blood flow information provided by the fMRIs. Participants’ level of satiety was significantly increased when they drank the glucose-sweetened beverages, but not so for the fructose-sweetened drinks. Although total calories ingested have the largest effect on body weight, hunger is a significant driving force behind the urge to eat and calories consumed. The inference being the less hungry you are, the less you will eat and the less weight you will gain.