Dr Erin Hanlon, University of Chicago
Have you been getting your forty winks? Because researchers have revealed this week that lack of sleep actually gives you the metabolic equivalent of the marijuana munchies, which could lead to unnecessary binge-eating. Erin Hanlon explained her research to Chris Smith...
Erin - Thereís an association between insufficient sleep, or short sleep, and the increased risk of obesity and thereís been some carefully controlled laboratories that have shown that when people are sleep restricted, they are reporting feeling hungrier and having a stronger appetite, most specifically for high carbohydrate and high fat foods. So we wanted to examine what might be causing this increase in appetite and further help to explain the current association with the increased risk of obesity following sleep restriction.
Chris - And just to be clear, the increased appetite thatís measured in these people; thatís not just because if youíre awake longer, youíre functioning for longer, you need more energy, therefore you compensate by eating more?
Erin - Correct. So the energy need of being awake longer is actually quite modest and studies have started to show that people are consuming more calories than are actually needed to maintain wakefulness.
Chris - So something else is going on, driving people who are in a state of sleep deprivation, to overeat?
Erin - Exactly. Thatís exactly itÖ
Chris - But we donít know what it is, as yet?
Erin - Right. Well we're starting to kind of tease those things apart. Itís probably a lot of things working in concert and our current study is adding to this growing literature and suggest one pathway by which this might be occurring.
Chris - What did you do to explore it and what is that pathway?
Erin - Right. So we brought people into the laboratory; we had then sleep either eight and a half hours a night or four and a half hours a night, and we examined a system that is involved in many areas. Itís involved in stress, the immune system, pain, reward and specifically reward driven eating or hedonic eating. So we explored this system, and itís actually called the endocannabinoid system. Following normal sleep, we found that blood concentrations of lipids that are involved in this system are low overnight and high during the day. When these individuals were sleep restricted, during the day those levels were even higher.
Chris - You are hypothesising then that those are driving the increased appetite that these people display?
Erin - Thatís what we think, because the endocannabinoid system has been known to be involved involved in overeating, and actually overeating highly palatable foods. So itís been thought that this system was involved in brain reward pathways and might affect eating behaviour via reward circuitry. So seeing this increase in blood concentrations suggests that this system might be overactive following a state of sleep restriction.
Chris - In other words, sleep restriction could be mimicking the marijuana munchies. The idea that people who use cannabis also tend to report getting hungrier, and eating more, and a tendency towards being overweight.
Erin - Exactly. So marijuana activates the endocannabinoid system as well. So we think that perhaps sleep restriction, just like marijuana usage, is activating the endocannabinoid system to cause overeating and overeating of highly palatable, rewarding foods.
Chris - Why?
Erin - I donít know.
Chris - What do we think the benefit of that is? Is that just because, if you are sleep deprived youíre more likely to be a bit less motivated, a bit more tired, a bit sluggish, therefore making sure you feel like you want to keep eating and stay at the top of your energy game, means youíre less likely to become someone else's lunch in our evolutionary history? Is that the idea?
Erin - It was probably protective at some point in a state of feast or famine, when you had to overeat to have energy stores for other times when you might not have access to food, but itís become a little bit maladaptive lately.
Chris - Where does this leave us then? What do we have to ask now, and does this help us to solve the problem for people who do gain weight because theyíre not getting enough sleep?
Erin - I donít think it will actually solve the problem but I hope it draws attention to the fact that sleep restriction and sleep deficiency is associated with a lot of negative outcomes and increased feeding just happens to be one of them. So, hopefully, this draws attention to the fact that we need to think of adequate sleep as an important aspect of maintaining good health and just as a byproduct of the day.