Galliott et al. published a 2007 article entitled “Self Control Relies on Glucose as an Energy Source: Willpower Is More Than Self Control” (pdf here). Recently Vaughan at Mind Hacks and Dave at Cognitive Daily have taken up the topic with some creative posts. Vaughan writes that Resisting Temptation Is Energy Intensive, focusing on the role of attention and the prefrontal cortices. Dave posts on Practicing Self-Control Takes Real Energy, and includes a recreation of the research procedure (with video) and an informative summary. I also mentioned some of this research in a previous post on Willpower as Mental Muscle.
What I want to add today is that this sort of research has implications for our understanding of brain evolution and for social problems like obesity and addiction. Focusing attention and using one part of your brain against another part, that takes significant energy. The brain is already our most energy-intensive organ, so adding the demands of “self control” on top of that is likely to have presented some adaptive issues in the past. Put differently, it’s unlikely to expect that we’ve evolved to be able to maintain self control over extremely long periods of time (say, months), simply because such problems rarely presented themselves in the past (there were few adaptive benefits) and because the energetic costs of doing so would have been quite high.
Diets are often marked by periods of effortful weight loss, followed by a slide back, where weight is regained. That pattern is not simply a matter of mind over matter, of willpower so we can match a cultural and cognitive ideal. It’s hard for people to maintain sustained mental efforts, it costs energy, and there’s little evolutionary reason to expect everybody’s brains to suddenly begin cooperating with what our culture tells us we should be able to do.