Does this sound familiar: you skip lunch, then later on, find yourself gobbling a lot more cookies or pieces of cake than you know you need, but somehow find it very hard to stop: and then spend the rest of the day beating yourself up about your lack of self-control and inability to maintain a healthy diet?
Well, by studying the effect of low blood sugar on self-control in dogs, a researcher at the University of Kentucky (UK) has come up with a possible explanation: the brain needs glucose to exercise self-control, and knowing this could help us make healthier choices in our diets.
Psychology graduate student Holly Miller said “it happens to everyone”, we eat more than we know we should when we are tired and low in fuel, “without fuel, you can’t inhibit the bad behaviour,” she added, “it’s physiology“.
This last remark is why Miller’s work is interesting, because scientists have long assumed that self-control, as in being able to delay gratification, requires a “sense of self” and is therefore more a matter of psychology, not physiology.
The idea is that we strive to achieve this ideal self and this takes effort: we have goals and aspirations and we “work” towards them, and sometimes this means delaying gratification in order to get there. You can see how this implies that energy, or some resource, is consumed in the striving. Such a concept of self-control clearly sets us apart from our four-legged friends.
Miller began to question this view when she attended a presentation given by Florida State University social psychologist Roy Baumeister, on glucose and self-control.
In a series of experiments that he performed on stage, Baumeister tested the effect of food-restriction on energy for self-control. Human volunteers were each given a pile of radishes and a pile of chocolate chip cookies, but were only allowed to eat one of them. They were then given puzzles to solve: the ones who ate the chocolate chip cookies spent longer trying to solve the puzzles.
Baumeister concluded that having to exert self-control (which he defined in the delayed gratification sense of having to do what one should as opposed to what one wants), resisting the cookies, caused the volunteers who were only allowed to eat radishes to use up more of the resource that is needed to maintain a sense of self.
Miller agreed with Baumeister up to a point: yes, maintaining self-control consumed some kind of resource, but its depletion had little to do with having to maintain a sense of self. Why couldn’t it simply be that the fuel, glucose, was consumed more quickly? In which case, wouldn’t a similar experiment with dogs, show this?
Miller had already been working with dogs and there was no shortage of canine “volunteers”. She completed two sets of experiments, which to onlookers must have looked like rather peculiar dog-training classes. These were reported in a paper published online in the journal Psychological Science in March this year.
In the first set of experiments one group of trained dogs was told to “sit and stay” for ten minutes, while another group of trained dogs was allowed to sit comfortably in a cage, either sitting or just staying, but without being “told” to do so (no “self-control” needed in the second group).
Both groups of dogs were then given food-related puzzles to solve (by the way, both sets of dogs were quite hungry by this stage). They had to retrieve treats from dog toys that they were familiar with (Tug-a-Jugs), except the toys had been altered so it was not possible for them to retrieve the treats.
Miller found that the dogs that had been told to exert self-control for ten minutes gave up quite quickly, in less than a minute, whereas the dogs that had not been required to exert self-control but sat or stayed in the cages kept going for more than two minutes.
These results paralleled those of Baumeister’s experiment, and led Miller to conclude it was nothing to do with a sense of self, but due to a physiological process: glucose depletion.
“Dogs don’t have a sense of self, or an ideal self, as far as we know,” said Miller.
“Doing this type of experiment with dogs allows us to explain the results in a less complicated way,” she added.
In the second set of experiments, Miller tested the results of glucose on self-control more clearly.
The dogs were again in two groups: one was given a glucose-based drink while the other was given a placebo: a sweet-tasting drink with no glucose. The dogs that had the glucose spent longer working through the puzzles.
Miller said her results showed that self-control does indeed correspond with diet, and that is why we should eat healthy foods like carrots and lean proteins that give us a long-lasting supply of glucose to keep the brain strong and help us resist unhealthy foods.
However, if you do fall off the wagon, says Miller, don’t despair: just because you “break down” and eat two pieces of chocolate cake, it does not mean you are a bad person or a hopeless case, “it’s purely physiological,” she says, and she finds this view helps her stop beating herself up as well.
“A lot of really determined people can get down on themselves about something like this,” said Miller.
“The truth is, if you push yourself to the point where you don’t have any resources, you can’t help it,” she added, explaining that perhaps more diets would succeed if we adjusted “our eating habits so that we can fuel our self-control more effectively in the future”.
Source: University of Kentucky.
Written by: Catharine Paddock, PhD