Your diet could make you dumber, a new study suggests. Using existing data and new experiments, researchers from Harvard University have determined that the cravings and psychological strains associated with limited food intake can have significant bearing on cognitive skills. The findings may inspire weight loss programs as well as global poverty and famine strategies.

The study is part of a broader research effort conducted by psychology professor Eldar Shafir of Princeton University and economist Sendhil Mullainathan of Harvard University. In Scarcity: Why Having Too Little Means So Much, the two analyze the psychological implications of shortage and deficiency in an attempt to understand why predicaments like loneliness, poverty, and hunger appear to perpetuate themselves. Drawing on new advances in behavioral science and economics, they formulate the “bandwidth” theory.

“Imagine that you are attending a late-afternoon meeting,” Mullainathan wrote in an accompanying piece in The New York Times. “Someone brings in a plate of cookies and places them on the other side of the conference table. Ten minutes later you realize you’ve processed only half of what has been said.”

According to the researchers, the cookie can be said to exceed the dieter’s mental bandwidth, as it demands a disproportionate amount of attention and self-discipline. The snack, like a looming deadline or an important speech, appears to problematize an otherwise simple task by creating a psychological crisis. In the face of scarcity, the imagined or actual emergence of what we need jams our mental abilities.

To test their hypothesis, the researchers examined scarcity and sufficiency in individuals rather than communities. Their research focused on Indian sugar cane farmers, whose personal economy tends to fluctuate with the seasons. As a result, the workers are technically both rich and poor during a given year.

“We measured farmers’ mental function — on what psychologists call fluid intelligence and executive control — one month before and one month after harvest,” Mullainathan explained. “And the effects were large: preharvest I.Q., for example, was lower by about nine to 10 points, which in a common descriptive classification is the distance between 'average' and 'superior' intelligence."

“To put that in perspective, a full night without sleep has a similar effect on I.Q.,” he added.

For this reason, many diets ultimately founder on a central paradox: dieting makes it hard to diet. To avoid the psychological strain and subsequent restriction of faculties, the researchers recommend that prospective dieters “economize their bandwidth.” A successful weight loss strategy usually involves as little thinking as possible, as constant real-time meal assessment and calorie counting tax both commitment and cognitive skills. This would explain the popularity and efficiency of the Atkins diet and other diets that impose general bans. 


Source: Mani A, Mullainathan S, Shafir E, Zhao J. Poverty Impedes Cognitive Function. Science. 2013.