why-sugar-makes-us-sleepy-and-protein-wakes-us-up

dleithaus

http://www.wired.com/wiredscience/2011/12/why-sugar-makes-us-sleepy-and-protein-wakes-us-up

There is a link inside the article to the original paper at the scholarly journal "Neuron"
http://www.cell.com/neuron/abstract/S0896-6273(11)00782-3

from the wired side......
John Updike, in his short story “Plumbing,” summarized human nature thusly: “We think we are what we think and see when in truth we are upright bags of tripe.” This is a tragic fact that we spend most our lives trying to forget. Although we like to imagine ourselves as the driver – our consciousness is in full control – that belief is a lovely illusion. In reality, we are mere passengers aboard the body, strapped to a fleshy engine that is driving us.

Consider the orexin system. 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. People with chronically low levels of orexin suffer from narcolepsy and obesity; many also have cataplexy, which occurs when the experience of strong emotions triggers a sudden weakening of skeletal muscles. (Laughter makes them go limp.) Studies have shown that injecting mice with orexin increases metabolism, largely because it makes the animals more active. The reverse is also true: low levels of orexin make people feel rundown and tired. This helps explain the mechanics of sleep deprivation, as keeping monkeys awake for extended periods all but silences their orexin cells. (However, studies show that the exhaustion can be quickly cured with an injection of the peptide.) In many respects, orexin acts like an internal gas pedal, as even slight twitches in the system can dramatically shift levels of activity.

The reason the orexin system is so important is that it links the needs of the body to the desires of the mind. 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. In other words, we get fat and sleepy simultaneously.

However, not every food has such perverse consequences. It’s long been recognized that meals high in protein are both more filling and less exhausting, which is why we’re always being told to snack on almonds and follow the Zone Diet, with its balance of carbs, protein and fat. (This study, for instance, found that protein rich breakfasts significantly improved cognitive performance.) Although the biological mechanism behind this dietary wisdom has always 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.....

[more on the link itself]