Effect Of Sleep Deprivation And Meal Timing On Insulin Sensitivity

As we continue learning more about the complexity of appetite and energy balance, sleep and circadian rhythm are emerging as important variables. Now a study by Robert Eckel and colleagues, published in Current Biology, illustrates how sleep deprivation and timing of meals can markedly alter insulin sensitivity. Studies were conducted in 16 healthy young adults (8w) with normal BMI. Following a week of 9-hr-per-night sleep schedules, subjects were studied in a crossover counterbalanced design with 9-hr-per-night adequate sleep (9-hr) and 5-hr-per-night short sleep duration (5-hr) conditions lasting 5 days each, to simulate a 5-day work week. Sleep was restricted by delaying bedtime and advancing wake time by 2 hr each. Energy balanced diets continued during baseline, whereas food intake was ad libitum during scheduled wakefulness of 5- and 9-hr conditions. Overall, the simulated 5-day work week  of 5-hr-per-night sleep together with an ad libitum diet resulted in a 20% decrease in oral and intravenous insulin sensitivity, which was compensated for by increased insulin secretion.. These changes persisted for up to 5 days after restoring 9-hr sleep opportunities. The authors also showed that shifting circadian rhythm resulted in morning wakefulness and eating during the biological night, a factor that may promote weight gain over time.   These findings have important implications not just for shift workers but for all of us, who may not be getting adequate amounts of restorative sleep. Paying more attention to sleep and its impact on appetite and metabolism may need to find its way into routine clinical practice. @DrSharma Vienna, Austria

Sleep Apnea And Quality Of Life In Iceland

This week, I am in Reykjavik on behalf of the Icelandic Medical Association to speak at their 2015 Annual Conference. Despite its proverbial rugged outdoorsy lifestyle with ample time spent in natural hot spring spas and saunas (both of which I enjoyed yesterday, thanks to my excellent hosts), Iceland has a significant obesity problem of its own – reason enough for this problem to be taken seriously (I will be meeting with the Icelandic health minister and his staff to discuss this issue later this week). There is indeed a small but active obesity research community in Iceland with growing experience in the management of this disease. One important contribution, for e.g. is the recent paper by Erla Bjornsdottir and colleagues from the University of Iceland, published in the Journal of Sleep Research, that examines the impact of two years of treatment vs. non treatment of moderate to severe obstructive sleep apnea (OSA) on quality of life in over 800 overweight or obese individuals newly diagnosed with this condition. The comparator group consisted of 750 randomly selected Icelanders. The researchers also compared users and non-users of CPAP treatment within the individuals diagnosed with sleep apnea. Overall, as one might expect, the quality of life (measured by the SF-12 questionnaire) of untreated individuals with OSA was markedly worse that of the general population, even when matched for age, body mass index, gender, smoking, diabetes, hypertension and cardiovascular disease. Surprisingly, however, despite a positive trend towards improvement in physical quality of life from baseline to follow-up in users and the most obese individuals, there were no significant overall differences between full and non-users. This is particularly surprising as I have often seen dramatic changes in the quality of life and general well-being in patients with OSA, who started on CPAP treatment in my practice (but I guess anecdotes are always tempered by averages). Based on their findings, the researchers conclude that the co-morbidities of obstructive sleep apnea, such as obesity, insomnia and daytime sleepiness (often not fully controlled by CPAP), appear to have a substantial effect on life qualities and may need to be taken into account and addressed with additional interventions. The message here, I believe, is that despite its effectiveness for better control of breathing, simply putting patients on CPAP and hoping for the best may not be quite enough to improve the substantially reduced quality of life associated with this… Read More »

Sleep Duration Strongest Predictor of Health Risk in Obese Teens?

If you had to guess the strongest predictor of cardiometabolic health risks in  obese teenagers, most of us would probably suspect their diet, sedentariness, or even mental health issues around mood, body image, or self-esteem. Few of us would have guessed sleep duration. But this is exactly what was found by Paul Gordon and colleagues from the University of Michigan, in a study published in the Journal of Pediatrics. Although relatively small (the study included just 37 participants aged 11-17), the researchers went to great lengths to objectively measure habitual physical activity and sleep patterns as well as a wide range of cardiometabolic risk factors. Amongst all of the measured variables, total sleep time and sleep fragmentation were inversely and independently associated with metabolic risk – the shorter the sleep time, the greater the risk. This relationship remained robust even when the data were adjusted for various measures of physical activity, anthropometry, and adiposity. Most subjects slept about seven hours a night, typically waking up at least once, with only five subjects getting the minimum recommended 8.5 hours of sleep each night. Given what we now know about the profound impact of sleep deprivation on metabolism, physical activity and eating behaviours, it is astonishing that so little attention is being paid to the issue of sleep both in the public discourse of obesity as well as in clinical management of excess weight. As I have said before, the three key drivers of obesity in my view are lack of time, lack of sleep and increased stress – everything else is either a consequence of or compounded by these factors. Is it time for doctors to begin handing out sleep prescriptions? @DrSharma Edmonton, AB

Why I Am Not Losing Sleep About NHANES’ Flawed Data

Regular readers may be well aware of the US-National Health and Nutrition Examination Survey (NHANES), the billion dollar juggernaut of a research enterprise conducted by the the US-CDC and the Department of Agriculture since the early 70s. It turns out that rather simple calculations, published in PLoS One by Edward Archer, from the Arnold School of Public Health at the University of South Carolina in Columbia, and colleagues, show that the dietary data collected in this survey (using a 24-hour recall), widely used by researchers and policy makers as the primary source of data on the impact of nutrition and diet on health, is rather “implausible”. As the calculations in the paper show, the caloric estimates that people are reportedly eating are simply not physiologically possible given their reported age, size, weight and levels of physical activity. In short, given the overall “iffyness” of the dietary information in NHANES, it is rather impossible to accurately determine the relationship between changes in caloric intake (and I would assume the same goes for nutrient composition) and the obesity epidemic. So, why do I not really care? For one, even if these data were fully accurate, knowing that Americans are consuming more calories today than they did before does not really tell me much – irrespective of whether or not these numbers have gone up or down, the fact is that somewhere along the line, the net amount of calories Americans consume is larger than the net amount of calories Americans need – probably by several hundred calories a day – end of story! Secondly, as in all observational studies, what you get are correlations,  which may or (more likely) may not give you useful insights into causality. Thus, as larger bodies need more calories to sustain (and larger people consume significantly more calories by just moving themselves around), I would expect average caloric consumption to have increased. Thus, even if we assumed for a minute that the obesity epidemic was caused by a viral infection that makes people fat, those larger people would now be eating more calories than before to sustain their larger bodies. Thus, showing that obese people eat more calories (which incidentally is not always the case), does not really provide much insight into what is causing the problem. Thirdly, we are dealing with population averages on an issue where we know there exists a rather wide range of… Read More »

Sleep Restriction Promotes Weight Gain in Humans

Regular readers already know that lack of sleep is increasingly seen as one of the major drivers of calorie overconsumption and weight gain. Those, who remain sceptical may be interested in a paper by Andrea Spaeth and colleagues from the University of Pennsylvania, just published in SLEEP. This, to date the largest randomised controlled trial of experimental sleep deprivation on eating behaviour shows that individuals who are sleep deprived will consume up to 500 extra calories per day compared to individuals who get adequate sleep. The researchers studied 225 health adults randomised 8:1 to an experimental condition (including five consecutive nights of 4 h time in bed [TIB]/night, 04:00-08:00) or to a control condition (all nights 10 h TIB/night, 22:00-08:00). Not only did sleep-restricted subjects gain more weight (0.97 kg) than control subjects (0.11 kg) but sleep-restricted weight gain was greater in African Americans than Caucasians and in males than in females. Sleep-restricted subjects consumed 30% extra calories (over 550 additional calories mainly between 22.00 and 04.00), easily accounting for the observed weight gain. Thus, the authors conclude that chronically sleep-restricted adults with late bedtimes may be more susceptible to weight gain due to greater daily caloric intake and the consumption of calories during late-night hours. Given what we know about how sleep deprivation affects appetite and metabolism, these findings should come as no surprise. Let us not forget that a key characteristic of “Westernised” society is significant sleep deprivation and about 40% of adult Canadians report at least one symptom of insomnia with over 10% of Canadians reaching for sleeping aids. Reason enough to consider sleep (or rather lack thereof) a key driver of the obesity epidemic. @DrSharma Edmonton, AB Spaeth AM, Dinges DF, & Goel N (2013). Effects of Experimental Sleep Restriction on Weight Gain, Caloric Intake, and Meal Timing in Healthy Adults. Sleep, 36 (7), 981-990 PMID: 23814334   .