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.
Now, Christophe Varin and colleagues from the Centre National de la Recherche Scientifique, Paris, France, in a paper published in the Journal of Neuroscience describe how glucose regulates key neurones in the brain to induce sleepiness.
Their studies in mice focussed on sleep-active neurons located in the ventrolateral preoptic nucleus (VLPO), critical in the induction and maintenance of slow-wave sleep (SWS).
Using both in vivo and ex vivo patch clamp studies, the researchers show that a rise in extracellular glucose concentration in the VLPO can promote sleep by increasing the activity of sleep-promoting VLPO neurons.
As the researchers note,
“The extracellular glucose concentration monitors the gating of KATP channels of sleep-promoting neurons, highlighting that these neurons can adapt their excitability according to the extracellular energy status… Glucose-induced excitation of sleep-promoting VLPO neurons should therefore be involved in the drowsiness that one feels after a high-sugar meal. This novel mechanism regulating the activity of VLPO neurons reinforces the fundamental and intimate link between sleep and metabolism.”
Apart from helping unravel the biology of a phenomenon that every parent of a young child is well aware of, this research raises a number of interesting clinical questions.
Does overconsumption of high-sugar foods necessitate counteracting these effects with caffeine? Is this why sugar-sweetened pop generally contains caffeine (to not put you to sleep)?
Does this also explain the practice of eating a bedtime snack to fight insomnia?
And what does this mean for people with poorly controlled diabetes: do they need to drink more coffee than people without diabetes to get through their day? (not something I’ve heard of).
For all my Canadian readers (and any international readers planning to attend), here just a quick reminder that the deadline for early bird discount registration for the upcoming 4th Canadian Obesity Summit in Toronto, April 28 – May 2, ends March 3rd.
To anyone who has been at a previous Canadian Summit, attending is certainly a “no-brainer” – for anyone, who hasn’t been, check out these workshops that are only part of the 5-day scientific program – there are also countless plenary sessions and poster presentations – check out the full program here.
To register – click here.
The title of this post may sound like a “no-brainer”, but the research literature on the long-term health benefits of weight loss from longitudinal intervention studies in people with severe obesity is much thinner than most people would expect.
Thus, a new study from our group, that looks at the relationship between changes in body weight and changes in health status over two years in patients with severe obesity enrolled in the Alberta Population-based Prospective Evaluation of the Quality of Life Outcomes and Economic Impact of Bariatric Surgery (APPLES) study, published in OBESITY, may well be of considerable interest.
As described previously, APPLES is a 500-patient cohort study in which consecutive, consenting adults with BMI levels > 35 kg/m2 were recruited from the Edmonton Adult Bariatric Specialty Clinic. The 500 patients enrolled were between 18 and 60 years old and were either wait-listed (n=150), beginning intensive medical treatment (n=200) or had just been approved for bariatric surgery (n=150). Complete follow-up data at 24 months was available for over 80% of participants.
At study enrollment, the proportion of patients who reported >2 and >3 chronic conditions was 95.4% and 85.8%, respectively. The most common single chronic conditions at baseline were joint pain (72.2%), anxiety or depression (65.4%), hypertension (63.4%), dyslipidemia (60.4%), diabetes mellitus (44.6%), gastrointestinal reflux disease (35.4%), and sleep apnea (33.5%).
After 2 years, just over 50% of participants had maintained a weight loss > 5%, with a mean weight change for the entire cohort of about 13 kg.
Losing > 5% weight was associated with an almost 2-fold increased likelihood of reporting a reduction in multimorbidity at 2-year follow-up, whereby outcomes varied between treatment groups: in the surgery group, the top three chronic conditions that decreased in prevalence over follow-up were sleep apnea (43% at baseline vs. 25% at 2 years,), dyslipidemia (60% vs. 47%), and anxiety or depression (59% vs. 47%); in the medically treated group anxiety or depression (69% vs. 57%) and joint pain (77% vs. 67%); and none in the wait-listed group.
As expected, any reduction in multimorbidity was associated with a clinically important improvement in overall health status.
In summary, this paper not only documents the considerable multimorbidity associated with severe obesity, it also documents the clinically important improvement in health status associated even with a rather modest 5% weight loss over 2 years in these individuals.
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 disorder.