May 21, 2013
John DiTraglia MD
Did you ever wonder why you’re not hungry in the morning when you wake up. Me neither. But if you had thought about it you would realize that it is strange. If you went eight hours during the day without eating you would be starving. And it’s not just that you are inactive when you sleep because most of the calories you burn in a day are for basal metabolism. If you had thought about this you might also ask whether there is something here that you could use in the afternoon to avoid being hungry and eating too much.
Some people at the Sleep Medicine Division of Harvard Medical School did think about this and decided to investigate. (1)
So thee possibilities suggest themselves: it could be that you eat a lot in the evening and that holds you over, or sleep suppresses appetite and you’re still sleepy in the morning or your bio-rhythm clock influences hunger. They decided to investigate this third possibility. They took 12 non-obese adults and staggered their sleep-wake cycles in the sleep lab and then monitored their appetite by questionnaire and by how much they ate in the various parts of the “day.” They found that the circadian rhythm of sleep wake cycles did indeed influence their appetite. So they were less hungry after the eight-hour sleep part of the cycle and most hungry eight to 10 hours into the wake part of the cycle. Appetite was not influenced by how much they ate altogether over 24 hours or kinds of food.
These authors didn’t measure them but they figure that neural and hormonal mechanisms must be involved in driving the rhythms of hunger and appetite.
How could this information help to explain obesity or treat obesity? There is a widely accepted negative correlation between sleep duration and obesity but either sleep or obesity could be either cause or effect and that correlation may or may not have anything to do with your bio-rhythms.
Also eating a lot in the afternoon and taking a siesta doesn’t represent a big change in this cycle.
Maybe you could try eating more, or at least something, in the morning when you’re not hungry and less in the evening when you are most hungry.
1. Scheer, FAJL, Morris CJ, Shea SA. The internal circadian clock increases hunger and appetite in the evening independent of food intake and other behaviors. Obesity 2013;21(3):421-3.