Your Money or Your Weight Loss

Monday, July 7, 2008 - 4:58pm

By Krista Scott-Dixon, PhD

Many years ago, my mother was desperate for me to pull up my socks and get better grades in school. One night, prompted by a couple of glasses of wine and my mediocre midterm results, she offered me $500 if I got all As in my final year of high school. Ever the business woman, I prompted her to offer $1000 for all A+. Spurred on by financial incentive, I managed very high As, and bargained her out of $750.

For most of us, money is a pretty good motivator. While not all of us are Gordon Gekkos from Wall Street, chanting “Greed is good” as we swindle others out of their dough, we are probably more likely to do something if there’s a pot of money at the end of it (or if by not doing it, we know we’re going to lose some cash).

A study published in September 2007 showed that people could be motivated by money to lose weight. Researchers compared three groups: Group 1 was offered no money; Group 2 was offered a modest amount of money, and Group 3 was offered the most money. Not surprisingly, the people offered the most money lost the most weight. This confirms the results of other studies that show people are more likely to do things like quit smoking if offered financial incentives.

But just how effective is a cash reward? The results of the weight loss study in September were pretty modest, and the biggest effect was in the short term. Three months into the study, Group 1 participants with no financial incentive lost 2 pounds, those in the so-so payback Group 2 lost approximately 3 pounds, and those in the best paid Group 3 lost 4.7 pounds. But after 6 months, when the financial gains were equalized, weight losses were similar across groups. In other words, not much of a difference in the long haul.

Indeed, some might consider saving their cash. A systematic review of the research on cash motivation for weight loss found that in all the studies examined, there was no significant effect of financial incentives on weight loss or maintenance at 12 months and 18 months. Nor was there much of an effect for group versus individual rewards, behaviour based rewards, or rewards handed out by various types of people (e.g. psychologists, employers). In other words, great idea for 3 months, but for long term weight loss and healthy weight maintenance, the wallet only goes so far.

Another recent study in the Journal of the American Dietetics Association suggested that money might only motivate certain things. In this study, researchers tried to combat the problem of people’s poor recall in accurately measuring eating habits, a problem that constantly plagues nutrition studies. (People are not very good at precise recollection of their food intake, just like they’re not very good at eyeballing straight lines when cutting.) In the study, participants were paid to accurately recall their diets -- in other words, to remember precisely what and how much they were eating. The researchers checked the participants’ saliva to see whether they were telling the truth. The smoking studies also found that although there was an effect of money among the people who quit smoking, only a small group actually did quit. In the case of the food reporters and non-quitters, cash made no difference at all!

So what works? Well, money does seem to work for a brief time. But if you’re looking for tricks to stay at a healthy weight for life, you might want to have more than a fistful of dollars.

Finkelstein EA, Linnan LA, Tate DF, Birken BE. A pilot study testing the effect of different levels of financial incentives on weight loss among overweight employees. Journal of Occupational and Environmental Medicine 49 no. 9 (Sept 2007): 981-989.

 Hendrickson S, Mattes R. Financial incentive for diet recall accuracy does not affect reported energy intake or number of underreporters in a sample of overweight females. Journal of the American Dietetics Association 107 no. 1 (January 2007): 118-121.
Paul-Ebhohimhen V, Avenell A. Systematic review of the use of financial incentives in treatments for obesity and overweight. Obesity Reviews (October 23 2007).   

Volpp KG, Gurmankin Levy A, Asch DA, Berlin JA, Murphy JJ, Gomez A, Sox H, Zhu J, Lerman C. A randomized controlled trial of financial incentives for smoking cessation. Cancer Epidemiology Biomarkers Prevention 15 no.1 (January 2006): 12-18.