Friday, December 09, 2011
Wired reports: [edited]
Secreted by a small cluster of neurons in the hypothalamus, orexin is a neuropeptide that regulates an astonishing array of mental properties, from sleepiness to hunger. Low levels of orexin make people feel rundown and tired.
Several studies have demonstrated that the intake of sugar can decrease the activity of orexin cells, which is probably why we want to nap after a carb heavy lunch. This phenomenon also begins to explain the downward spiral of obesity triggered by our warped modern diet. Because we eat lots of refined sugars, washing down Twinkies with cans of Coke, we continually reduce levels of orexin in the brain, which then reduces levels of physical activity.
It’s long been recognised that meals high in protein are both more filling and less exhausting. Although the biological mechanism behind this dietary wisdom has been unclear, that’s beginning to change – we finally understand why consuming protein can be an effective weight loss tool. The answer returns us to orexin.
According to a new paper in Neuron led by scientists at the University of Cambridge, consuming foods high in protein can increase the activity of orexin neurons. This, in turn, leads to increased wakefulness and bodily activity, helping us burn off the calories we just consumed. Furthermore, eating protein in conjunction with glucose can reduce the inhibitory effects of sugar on orexin.