title: Is raised blood glucose associated with the relief of tension? Blood Glucose and Subjective Energy Following Cognitive Demand
abstract: A series of three studies examined the influence of  glucose drinks  and increasing blood glucose levels  on  mood .  Experiment one considered the short-term effect of a glucose containing drink on mood in young adults : a glucose drink in the morning and higher blood glucose levels were both associated with feeling less tense . Higher blood glucose was also correlated with greater self-reported energy . In the second experiment high blood glucose levels were sustained for 2 hr by repeatedly taking a glucose containing drink . Again higher blood glucose levels were associated with reports of less tension . In a final study subjects were placed in a frustrating situation . The consumption of a glucose drink result ed in fewer negative responses , following a negative statement from the experimenter , in subjects who had fasted over-night . It was concluded that higher blood glucose levels are associated with feeling less tense Previous studies have found a small association between the level of blood glucose  and subjective reports of energy in those sitting quietly . Given reports that both memory and attention are influenced by the level of blood glucose it was hypothesised that under conditions of cognitive dem and there would be a stronger association between mood and blood glucose levels . In three studies , with three cognitive tasks , the Stroop Task , Rapid Information Processing Task , and a difficult test of h and -eye coordination , falling blood glucose was associated with feeling less energetic
target: The authors even suggested in this case increasing educational levels as a means of reducing obesity .
  Indeed , we have recently reported results from two experimental studies showing that mental work up-regulates appetite-stimulating hormones and promotes overconsumption of food ( 3,4 ) .
  Furthermore , a careful examination of our data revealed that when the subjects were categorized on the basis of the mental workload intensity , those for whom the intensity of the mental effort was greater significantly increased their spontaneous food intake as compared with those characterized by a less strenuous cognitive effort .
  In other words , the harder we think the more we eat .
  This hyperphagic effect of intense thinking was also accompanied by more plasma glucose instabilities ( 5 ) .
  The fluctuations in plasma glucose levels that were observed are in agreement with the literature showing that a period of intense cognitive processing leads to a measurable decrease in levels of blood glucose ( 6 ) , a fall that has also been associated with feeling less energetic ( 7 ) .
  Accordingly , food intake might be perceived as a strategy for allowing the individual to recover optimal body functioning .
  These observations are also relevant for students having hard times to learn at school and for whom study ing is arduous and mentally challenging .
  On the basis of our observations , we find it realistic to postulate that those susceptible to commit more cognitive effort to take in charge st and ard mental tasks are more likely to over-eat and gain weight compared with those for whom the accomplishment of mental tasks at the same level of performance is elementary or more natural .
  Along the same lines , it would not be surprising to find a higher dropout rate for those ‘ mentally stressed ’ students .
  In a system where academic performance continues to rank as high priority in public schools , it seems obvious that some students are genetically more gifted and likely to perform at a higher level ( 8) .
  As previously shown , better cognitive abilities are predictive of more important life achievements such as earning a doctorate , securing a patent , or publishing a novel or major literary work ( 9 ) .
  It may be somewhat paradoxical that the amount of knowledge-based work is more important in the higher socioeconomic groups whereas population data show a higher prevalence of obesity for the socioeconomically disadvantaged .
  Thus , individuals highly involved in mental work are not all likely to over-eat and other healthy behaviours such as regular physical activity may counterbalance the net impact on energy balance .
  As mentioned in the paper by Yu and co-workers ( 1 ) , educational attainment seems to be an important mediator of this relationship .
background: In an early view issue of this journal , Yu and co-workers ( 1 ) published a systematic review and meta- analysis about the mutual relationship between obesity and intelligence quotient ( IQ ) .
  The authors observed that a lower IQ score in childhood was associated with obesity in later adulthood .
  Although it is not possible to definitively rule out reverse causation in the IQ – obesity relationship , two main mechanisms have been put forward by the authors that could explain why a low IQ has been found to be a predictor of obesity .
  First , higher intelligence may reduce the risk of obesity by promoting more healthful behaviours .
  For example , data from a cohort study showed that children with higher mental ability scores reported significantly more frequent consumption of fruit and vegetables and more high-intensity physical activity participation in adulthood ( 2 ) .
  Second , higher childhood IQ may predict favourable socioeconomic positions later in life .
  With the advent of computers and new technologies , the pendulum has swung far in the direction of excessive mental activities , as opposed to excessive physical activities .
  A careful examination of computer-related activities reveals that they represent a particular type of sedentary activities ; they are stressful and biologically dem and ing for the body and deserve to be counterbalanced by an adequate physical activity regimen ( 10 ) .