Even among academic researchers who study weight, obesity, and nutrition, that is a question that's been looked at infrequently. "I agree that this is an understudied issue," says James O. Hill, the executive director of the University of Colorado's Anschutz Health and Wellness Center and the co-founder of the National Weight-Control Registry (NWCR). Established in 1994, the registry has served as one of the largest fonts of information about successful weight losers, continually recruiting individuals who are at least 18 years old and have lost at least 30 pounds and kept them off for more than a year. Once enrolled, members are given extensive questionnaires and annual follow-up surveys on their weight-loss strategies as well as behavioral and eating habits.
Much of the work conducted by obesity researchers has centered around the intricacies of how and why people become obese and overweight, how and if excess weight is detrimental to health, and how to lose it. But there has also been a little exploration into how weight loss could affect the mind.
An extensive 2011 review of different weight-loss methods by Anthony Fabricatore, an assistant professor of psychology at the Perelman School of Medicine at the University of Pennsylvania, and others found that obese people generally experienced decreased symptoms of depression after taking part in a weight-loss trial. As noted in the review, that conclusion provides a sharp contrast to studies conducted throughout the 1950s. In a 1957 paper, AJ Stunkard—an eventual pioneer of obesity research—wrote that "for a large number of overweight persons, the current prescription of reducing diets has had unfortunate consequences; for a smaller number, it has been disastrous." These consequences included depression, anxiety, and even psychosis.
It appears that over the years, though, these obesity-treatment programs adopted a more balanced approach to weight loss. In a 2014 study examining the Look AHEAD project—an eight-year-long randomized, controlled trial of intentional weight-loss interventions, including diet and exercise, aimed at obese individuals with type-2 diabetes—the researchers concluded that the incidence of depressive symptoms were significantly lower among the treatment group than in the control.
But most people who try to lose weight are not surrounded by a team of health professionals. And the few attempts to look at a more representative slice of weight losers have presented some very counterintuitive findings.
Last August, a team of researchers delved into the English Longitudinal Study of Ageing (ELSA), a U.K.-based dataset keeping track of people 50 years old and above, updated every two years. The team was following up on earlier population studies that had found a negative association between weight loss and depressed mood. Though they were intrigued by the results, they also felt that these studies had too broad a focus, having included people who were at an ideal weight to start with and whose subsequent weight loss might indicate underlying health issues.