Prehistoric instinct could explain mystery of glucose-boosted self control

The paper – by Dr Neil Levy of Macquarie University, Australia – proposes that tasting glucose tells the brain it is in a resource-rich environment, where food is readily available.

Any opportunity to consume a sugary snack therefore becomes less urgent to the subconscious mind than it would be if sugar is restricted, which signals to the brain that less food may be available.

Speaking to FoodNavigator, Levy said the constant deprivation associated with dieting may trigger prehistoric instincts which override the conscious effort to avoid snacks.

“Our minds are adapted to an environment where food is precarious,” ​he said. “We’re not designed for this environment, we’re designed to be hunter-gatherers on the Savannah.”​

Levy added he is hopeful taking some glucose could help boost self control, noting: “Dark chocolate is relatively healthy and if it turns out a square of dark chocolate in the late afternoon could really make controlled eating much easier it would be great.”​

Yet he conceded that, although there is evidence glucose boosts self control, it is possible giving a person some sugar may not improve willpower and that further testing must be done.

“We need to get the signal that food isn’t precarious, but we know lots of signals don’t work,”​ he said. “If the signal is easy to give then there wouldn’t be a problem.”​

Levy now hopes a psychologist will take his theories from the Philosophical Psychology ​article​​ and run some studies, noting several have already been in touch.

A dual task paradigm with every study participant performing two tasks – one which depletes self control then a dependent measure testing whether the addition of glucose has helped – along with a control group which has no glucose would be a good design option, he said.

Exploit or explore instinct​

Levy’s theory – a variation of others in the ‘opportunity-cost’ model – rivals the widely held ‘ego depletion’ paradigm. Ego depletion suggests self control relies on the presence of glucose as a car relies on fuel, and once glucose is depleted control runs out, Levy explained.

However, he said the ego depletion model is flawed since several studies proved swishing around a sugary drink in the mouth without swallowing still improves self control over snacking, therefore discounting the petrol tank analogy.

Nevertheless, though the reasoning remains a mystery, Levy noted in the article that glucose administration does seem to improve self-control, drawing from a host of other studies including a 2007 Gaillot et al. study​​, and Baumeister and Tierney’s 2011 book ‘Willpower: Rediscovering the greatest human strength’.​ Baumeister’s previous studies show glucose’s ability to boost self control cannot be not replicated with artificial sweeteners, Levy said.

“We know people and animals are sensitive to all kinds of signals,”​ Levy said. “Glucose is a signal – one of a number – of availability of resources. It’s basically a signal that says ‘relax you don’t need to grab the cookie in front you right now, you don’t need to exploit you can explore’. The costs of exploring aren’t too high.”​

“There is the perennial problem all animals face in how to allocate resources. When to start looking for new food, when to move on to new patch of food when there is a diminishing food patch - it’s an explore or exploit problem.”​

Levy added that a large part of these explore or exploit decisions are unconscious calculations, noting this is the reason people have such difficulties sticking to restricted diet goals.

Source: Philosophical Psychology​

Published online ahead of print, DOI: 10.1080/09515089.2016.1173202​

The sweetness of surrender: Glucose enhances self-control by signaling environmental richness​

Author: Neil Levy