Many of us have been hearing the “weight-loss hormone” story for a while. If you are sleep deprived:
- Your body makes more ghrelin, the hormone that says “GO, eat more” and ...
- Your body makes less leptin, the hormone that says “STOP,” and tells your body it is full, and ...
- Your body makes more cortisol, which can increase your appetite.
But the recent question Dr. Oz asked me was critical to everyone’s better understanding of the relationship between sleep and weight loss: “I would think that that anytime I am awake I would burn more calories. Why isn’t this the case?”
It all has to do with our stages of sleep, specifically REM sleep.
During REM sleep your brain is more active than any other stage. In fact, in some cases, it is more active than when you are awake. This activity requires fuel for thought, called glucose, the basic building block of most foods.
Sleep follows a very particular, and fairly predictable, cycle in most individuals each night:
Your brain goes from: Wake to Stage 1, from Stage 1 to Stage 2, from Stage 2 to Stages 3 and 4, back to Stage 2 and on into REM sleep. You can see this in the graph above. But look at the yellow bar. This represents REM sleep, and notice how it gets longer and longer as the night progresses. This shows how your body gets more REM sleep in the very early morning hours. Just like riding a bike uphill, you have to climb up before you can coast down that hill, and you need to go through the first few sleep cycles to get more REM sleep.
So, what happens when you only get 6 hours of sleep? You cut off that last REM period, which is where your brain uses the most calories. What does that mean for your waistline? Over the course of a year, one research study from Sao Paulo showed this could add up to as much as 14 pounds of extra weight.