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Mind over matter: Perceived time as opposed to real time on blood glucose in type 2 diabetes

To most experimental human biologists, among whose company I include myself, life, in its most basic form, is a series of biological steps, relentless biological steps but beautifully masterminded by genes, orchestrated by hormones and managed by enzymes. These biological steps are shaped by our biological clock, our age, our sex, and by a myriad of inherited factors. They are also shaped by the food we eat and the drugs we take which together, dominate human biology experimental studies.  From time to time, we face assertions that biological processes can be mastered by mental power. We accept that relaxation causes biological effects but do so with the same thought process that tells us that physical activity causes biological effects. We even accept that relaxation can be trained to quite high levels through techniques of, for example yoga or other forms of meditation. The neurological systems are very complex and thus those not expert in the field of neurobiology simply accept such findings on trust.

Now data is beginning to emerge that one of the most measured aspects of life, blood glucose, might be somehow subject to forces other than food, exercise, drugs, disease and other such tangible matters. We are now beginning to see mental forces enter this once biological citadel. This summer, a paper[1],[2]appeared in the highly rated scientific journal, “The proceedings of the National Academy of Sciences (PNAS)” which opens up a whole new vista on mind and biology.

Volunteers suffering from type-2 diabetes (the type associated with obesity as a causative factor) were recruited. All were receiving dietary management therapy and also they were taking metformin as a medical treatment to manage their diabetes. Prior to the study, they were asked to monitor their blood glucose levels before and after every meal and to create a diary of blood glucose fluctuations. Thus they were trained to fully understand their own blood glucose measurements. On the morning of the study, they were asked to arrive having fasted for at least 8 hours. They were asked to hand in phones, watches and anything else that could be used to monitor time such as fit-bits, bleepers, computers, etc. They were also asked to hand in all medication. Now they were ready for the study, which quite frankly was straightforward: sit, relax and watch videos, changing the video every 15 minutes (the actual changing of the video was done by the research staff so the volunteers simply sat and relaxed).

Having taken away all time-related devices, the subjects were left with just one indicator of time, a wall clock. And herein lies the rub. The true time spent by each group was 90 minutes. However, two groups were tricked. For one third of the subjects, the clock was set perfectly accurate and when the allotted 90 minutes was up, they could see so on the clock. For the other two groups, the clock was rigged. For half, it ran twice as fast as it should in reality and for the other, it ran half as slow as reality. Thus one group spent the true allotted 90 minutes in the test. For another group, the test lasted just 45 minutes and for the third group, the time taken was 180 minutes. Blood samples were taken before and after the test and the drop in blood glucose noted. At the conclusion of the test, the subjects were asked to state how long the study lasted and they all more or less agreed with the clock, even though all of them had just spent 90 minutes under the the test conditions. They did not differ in terms of perceived stress but hunger ratings did differ. Those with the fast clock showed the highest level of hunger compared to those rigged to imagine a longer time period. The critically important finding was that the blood glucose levels were dramatically altered by the covert manipulation of time.

Perceived time
Real time
Blood glucose
Decrease over the study (milligrams per deciliter)



The authors conclude thus: “Our findings that the mind can actually adjust the body’s glucose suggests new avenues for treatment and prevention”.  The study was well conducted by experts in psychology from Harvard and Milan. But at the end of the day, experimental biologists should really not be surprised. We use placebo treatments in our study and expect always to see some placebo effect albeit very differently fro the true treatment effect. But it does reinforce the need to have much stronger links between the biological and behavioural sciences.

Note: Almost 60 years ago, in a review in Science[3], the effect of tricking people on time as regards appetite were reported by the great Stanley Schachter at Columbia and these effects are covered in a chapter in my new book on obesity. The dictum that “an hour in the library saves days in the lab” still rings true!

My new popular science book on obesity: "Ever seen a fat fox ~ Human obesity explored" is outlined
on my blog of Tuesday, May 17th, 2016 and at UCD Press

[1] Park C et al (2106) PNAS, 113, 8169-70
[2] I am grateful to Professor Bobby Cheon of Singapore’s A*STAR nutrition group for pointing out this paper to me and I look forward to blogging on his forthcoming studies

[3] Schachter S (1968) “Obesity and eating: the internal and external cues differentially affect the eating behaviour of obese and normal subjects” Science, 161: 751-6


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