What Willpower Has to Do with Cookies (and Kale, Too)

Glucose can help you negotiate a raise, make firm decisions, and say no with minimal waffling.

Mardi Gras and willpower: they’re not meant to be in the same sentence – or the same celebrating street.

Falling just before Lent, the period in which Catholics traditionally shun things like alcohol, sweets, meat, or other temptations, Mardi Gras originated as a kind of prophylactic against indulgence. The logic was this: by sloshing around in a days-deep pool of indulgence, a person would be able to get cravings for those things out of his system. Post Mardi Gras, he’d emerge with willpower of steel and ready to take on 40 days of lean times and clean living.

Mardi Gras logic probably springs from the same commonly-held notion that willpower can be replenished or strengthened by doing something pleasurable and relaxing, like reading the newspaper or watching a movie.

And yet, recent studies have shown that dives into hedonism and long bouts of relaxation don’t actually fortify willpower. What does? Sugar. Specifically, your blood glucose levels.

Roy F. Baumeister and John Tierney’s recent book Willpower cites new studies on the link between willpower and glucose levels. People who ingested a tasteless but sugary concoction performed just as well in subsequent feats of willpower as did those who were fed delicious ice cream. Both of these camps did far better than those who performed leisure activities, like reading the newspaper, first. How much pleasure or relaxation we’ve banked, as through enjoying ice cream or reading a good book (or days of Mardi Gras partying) doesn’t support self control. But keeping your glucose (blood sugar) levels at an optimal level does.

Lest you get too excited, this isn’t a green light to binge on Twixes and cupcakes, which is actually terrible for your midterm willpower. Stable blood sugar actually favors healthy foods like eggs, nuts, and veggies.

Take it to work: The applications of this knowledge to your day-to-day are quite clear: make sure that you’ve fuelled right for the task at hand. If you’re going to need to make important decisions at a meeting, or negotiate your salary in a review, eat first or bring a snack. It might help you make the best decision of your life.

Read more about how to fortify your willpower in Baumeister & Tierney’s new book. You can also check out the 12-minute summary here, on Blinkist.