I noticed this news story yesterday, which reports on research published recently in the journal Obesity. The research, from Sweden, assessed the effects of sleep deprivation on food purchasing [1]. Fourteen men were given about $50 to spend on food in two settings: once after the men had a full night’s sleep, and once after a night of complete sleep deprivation.
In each setting, men were given a set breakfast in the morning to negate the effect of hunger on food purchasing decisions. During the shopping exercise, the men had had access to 40 items selected by the researchers. Half of these were ‘high calorie’ (> 2 calories per gram) and half of which were ‘low calorie’ (< 2 calories per gram). The study subjects were asked to purchase as much food as they could with the money they had available.
The results showed that after the night without sleep, the men purchased food that was more calorific (9 per cent more).
The researchers also measured levels of the appetite-stimulating hormone ghrelin in the morning. This was higher in the morning, overall, after the night without sleep. However, ghrelin levels did not correlate with purchasing decisions, so the higher levels of hormones is unlikely to explain the effect of sleep deprivation on the purchasing decisions.
This study is of some interest, I think, but is just part of a considerable and expanding body of evidence which suggests that sleep can influence body weight and composition. Sleep deprivation has been found to induce, among other things:
- An increase in levels of inflammation in the body [2]. Inflammation in the body may participate in the poor functioning of hormones such as insulin (insulin resistance) and leptin (leptin resistance) – both of which are implicated in obesity. In one study, just one night of about 4 hours sleep was enough to impair insulin functioning [3].
- Raised levels of the hormone ghrelin [4], as was observed in the latest study.
- Lowered levels of the hormone leptin (an appetite-suppressing and metabolism-boosting hormone) [5].
- Increased hunger. In one study, stopping men sleeping for a single night led to them eating significantly more the following day [6].
- Increased levels of the stress hormone cortisol [7] (excess cortisol can cause fat deposition, usually around the midriff).
- Reduced metabolism of fat. In one study, disrupting men’s sleep with an alarm clock and allowing them only an average 6½ hours sleep, compared to no alarm clock and 8 hours sleep, caused their metabolism of fat of to fall by two-thirds [8].
- Changes in body composition. In one study on the impact of sleep on weight loss, shorted sleep was found to reduce fat loss but increase muscle loss [9]. This effect may have something to do with the ability of sleep deprivation to increase levels of cortisol, as this hormone predisposes to fat gain and muscle loss.
Perhaps not surprisingly, some researchers have suggested changing sleep patterns over recent decades might be an important but under-recognised factor in the burgeoning rates of obesity and chronic disease [10]. I’m inclined to agree with this, and believe that going chronically short on sleep is a potential hazard that many of us can do something about.
I’ve found it can help a lot of people to reconsider their habitual bedtime, and just shift this forward a bit. This does not have to be every day and does not preclude people from having occasional late nights. It maybe means that if someone feels they do run short on sleep (and many people I work with do), they might consider going to bed maybe an or so hour earlier than they usually do.
One mental trick that can help here is not to view sleep as ‘unproductive time’, but as a core lifestyle habit that is important for both restoration of energy and general health and wellbeing. That way, sleep looks less like a ‘waste of time’ and more like something worthwhile properly investing in.
References:
1. Chapman CD, et al. Acute sleep deprivation increases food purchasing in men. Obesity (Silver Spring). 2013 Aug 1 [Epub ahead of print]
2. Meier-Ewert HK, et al. Effect of sleep loss on C-reactive protein, an inflammatory marker of cardiovascular risk. J Am Coll Cardiol 2004;43(4):678-83
3. Donga E, et al. A single night of partial sleep deprivation induces insulin resistance in multiple metabolic pathways in healthy subjects. J Clin Endocrinol Metab. 2010;95(6):2963-8
4. Schmid SM, A single night of sleep deprivation increases ghrelin levels and feelings of hunger in normal-weight healthy men. J Sleep Res 2008 Sep;17(3):331-4
5. Spiegel K, et al. Impact of sleep debt on physiological rhythms. Rev Neurol (Paris. 2003;159(11 Suppl):6S11-20
6. Hogenkamp PS, et al. Acute sleep deprivation increases portion size and affects food choice in young men. Psychoneuroendocrinology 2013 Feb 18 [Epub ahead of print]
7. Reynolds AC, et al. Impact of five nights of sleep restriction on glucose metabolism, leptin and testosterone in young adult men. PLoS One 2012;7(7):e41218
8. Hursel R, et al. Effects of sleep fragmentation in healthy men on energy expenditure, substrate oxidation, physical activity, and exhaustion measured over 48 h in a respiratory chamber Am J Clin Nutr 2011;94(3):804-8
9. Nedeltcheva AV, et al. Insufficient Sleep Undermines Dietary Efforts to Reduce Adiposity. Ann Intern Med. 2010;153(7):435-41
10. Van Cauter E, et al. Metabolic consequences of sleep and sleep loss. Sleep Med 2008;9 Suppl 1:S23-8
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