Glucose and Self-Control

Calorie restrictive (CR) diets have plagued our nation. You want to lose weight, eat less calories. While it is true that calorie intake will decrease body fat percentage, it may not be the most effective way due to lack of adherence.

Many people enthusiastically embark on their journey to weight loss and have great success in the beginning. But as time goes on, saying “no” to that delicious piece of cake becomes harder and harder, especially when tempted by a second or third offer. This diminishing self-control effect can even be seen within the time frame of a single day—people start their mornings off successfully, and continue success throughout the day, but once the sun sets their night eating and cheating behavior comes out.

Self-control is the ability to override one’s thoughts, emotional urges, and behavior.  It has traditionally been associated with motivation or motivational deficit, that is low motivation is associated with low self-control and vise-versa. However, more often than not, CR dieters maintain their desire and motivation to lose weight but struggle with the self-control to do so.

Cognitive psychology researcher, Matthew Gailliot, and his colleagues resolved this conundrum by discovering the important role of glucose has on self-control and brain functioning.

Glucose is the main type of sugar in the body and primarily acts as the energy source to the brain. Although the brain only constitutes 2 percent of a person’s body weight, it uses 75 percent of glucose intake to complete any task of controlled effortful processing, such as cognitive, behavioral, and emotional regulation.  It is, therefore, considered a metabolically expensive organ.

Gailliot conducted a series of nine different experiments to observe his participants’ performances on a variety of self-control tasks in relation to glucose levels and manipulations. He found that self-control tasks use up a lot of glucose and participants with less glucose after an initial self-control task performed worse of subsequent self-control tasks. Gailliot also found that the brain consumes more glucose for self-control tasks when changing a habit has low levels of personal importance and high requirements of self-regulation effort. Lastly, he found that by replenishing some participants with glucose (sugar) after their first self-control task, they performed better on a second self-control task in comparison to a group of participants who were given a placebo (splenda).

So, what does this mean to CR dieters?

Gailliot’s studies showed how highly susceptible self-control is to fluctuations in glucose. Restricting calorie intake may be what is sabotaging CR dieters’ glucose levels, self-control, and ability to adhere to their dieting rules. Self-control operates as a limited resource, consumed and expended in the process. This is why dieting failure is most likely to occur at night, when glucose storage is used least effectively, and why it is harder to refuse multiple offers of tempting food. It also helps explain why CR dieters’ self-control diminishes over the course of their diet as they consume and store less amounts of glucose.

These studies also suggest as to why CR diets fail simply due to their nature. Many CR dieters use zero-calorie sugar substitutes, like Splenda, to help reduce their total calorie intake. Along with the many other nutritional issues of Splenda and zero-calorie sweeteners, Gailliot clearly illustrates that Splenda is not a form of glucose and therefore cannot and will not replenish the fuel needed to control food choices in tempting situations. Also, CR diets are often lack internal motivation and require high amounts of self-regulation. People use CR diets to lose weight often for health reasons or aesthetic reasons, but rarely for the personal enjoyment and ithe mportance of dieting. The self-regulation tasks used to determine calorie consumption, such as counting calories, require high amounts of cognitive effort. Therefore, the rules and structures of CR diets alone use up great amounts of glucose, leaving lesser amounts for control.

Contrary to the media and pop-culture diets, there is not a sure way to “think” or motivate ones self to thinness. While motivation may aid in the process, Gailliot proved that self-control is more than just a metaphor for motivation—it has strong physiological correlates with glucose. Non-adherence rates in CR dieting reflects an impairment in the capacity to perform a controlled behavior or resist temptation, not in the dieter’s lack of desire. This does not mean that a massive sugar load will help your dieting efforts, but rather, balancing your blood sugar and maintaining the body’s natural homeostasis through foods that are moderate to low on the GI index may best increase your dieting success.


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