Insulin: Appetite Suppressant? Researchers Say Maybe

First study of insulin's direct effect on behavior
By Elizabeth Armstrong Moore,  Newser Staff
Posted Jul 21, 2017 8:44 AM CDT

(Newser) – Even people who don't have diabetes may some day take insulin if the findings from a small new study hold. Researchers report in the journal Nature Communications that, in what may be the first study to look at how insulin impacts behavior, the hormone may suppress one's appetite. The team studied 28 volunteers with insulin sensitivity (that's most people), and 20 who are resistant to insulin (this is more common as we age). Using fMRI, scientists watched the participants' brains after they fasted for 10 hours overnight on two occasions and then inhaled either a nasal spray or placebo. Researchers found that those with normal insulin sensitivity enjoyed images of food 5% (and sometimes 27%) less after inhaling insulin than after taking a placebo. Their brain activity confirmed these results.

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Normally, when we see tasty food, our brain's reward pathways are triggered and dopamine is released, which motivates us to find food. Insulin, the neuroscientists hypothesize, could be weakening this reaction, reports Popular Science. Extra insulin in the brain could disrupt communication, meaning dopamine might have a harder time getting cells to transport it. The therapy didn't work on people with insulin resistance, and in a few instances resulted in people in this group craving food more. Popular Science's headline reads, "Sniffing insulin might help people eat less," and it explains why inhaling it is preferable to injecting it in this situation: The former dispenses it quickly to the central nervous system; the latter meddles with blood-sugar levels. (Some call dementia a type of brain diabetes.)

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