When we skip a meal or get very hungry, the desire to stuff down really fattening food becomes irresistible. Last week I published a blog about how to remain calmer and resist the doughnuts – by including some fat in our diet. This week, I will cover why getting very hungry makes us even more prone to a bit of biscuit bashing. And it seems its all to do with that pesky hunger hormone, ghrelin.
So they got a bunch of rats and some they starved and some were injected with ghrelin. This led the rats to poke their noses harder and harder on the feed button that released their high fat chow. They also pressed the lever that gave them sucrose (sugar). Some other poor rats had their ghrelin receptors deleted, and these rats did not go for the high fat chow or the sucrose when hungry, just their ordinary chow. What the scientists are working on
We suspect that during evolution a link between stress, ghrelin and eating behaviors may have instilled an important survival advantage. 1
Fortunately for the rats, the scientists also experimented on humans. They administered them with ghrelin, then laid them in a MRI scanner and showed them pictures of food. They found
ghrelin administration to human subjects during functional magnetic resonance imaging increases the neural response to food pictures in brain regions implicated in hedonic feeding, confirming its importance in human appetite regulation.
Or, in plainer English, if we want to binge on cakes, just get hungry. After all, we are millions of years old (some mornings this feels individual) in evolution and until very recently, food was not always readily available. So if we got very hungry and some food came to hand, we stuffed as much of the really fattening stuff down our gobs as we possibly could, since we were never sure when the next bonanza would come by. Rule number one therefore is to avoid kicking off the feast or famine cycle: there is never any need to get seriously hungry these days.
More was discovered – and that was the effect of stress on ghrelin. And here things got rather interesting; when stressed, the amount of ghrelin in the brain increased, making us feel hungrier, but at the same time, less depressed. Our dopamine goes up, the upshot of all this meaning we feel more cheerful when we go out hunting, the dopamine makes us want to go out hunting. I just love dopamine. It is the neurotransmitter of reward, of the desire to go get ’em. Low dopamine means lying in bed with no will to leap forth and face the day. So get stressed and hungry and we happily go hunting for the biggest cream cake in the shop. Get stressed, and we start blissful dreams of crumpets dripping with butter.
For some, this offers an explanation as to why so many now battle with excess baggage around their middle. Our lives are unbelievably stressful. We rush from pillar to post; our children are rushed after school from activity to activity; if we aren’t busy, we aren’t important. We neglect our sleep – very unsexy to go to bed early. And we have forgotten how to eat, grabbing convenience pre-prepared food has become the norm. Added to all this is the toxic world we live in. Trust me, we are stressed. Added to those stressors is our despair at our burgeoning bottoms, so we either skip breakfast or lunch, making ourselves hungry and even more stressed. Next on the things to do list: food shopping. And whilst squeaking the trolley around the supermarket, we see the wondrous lemon drizzle cake and we are immediately enslaved by our old survival adaptation and simply have to lurk around the corner, waiting for our moment to hunt it and eat it.
- Chuang J-C, Perello M et al. J Clin Invest. 2011 July1; 121(7):2684-2692 [↩]