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Obesity, delayed gratification and the Marshmallow Test

September 1st, 2011

A new follow-up to the famous Marshmallow Test study on delayed gratification has just been published. Back in the 1960s, researchers tested a group of pre-school children on how long they could resist the temptation of an immediate reward (e.g. a marshmallow) in favour of a “larger, later” reward (e.g. two marshmallows). They followed these kids for decades, and found that the kids who were able to hold out the longest ended up less vulnerable to outcomes ranging from obesity to divorce to crack cocaine addiction.

The newest update, just published in Proceedings of the National Academy of Sciences (full text freely available here, press release here), with the subjects now in their 40s, confirms that the kids who were “high delayers” are still “high delayers,” and the kids who were “low delayers” are still “low delayers.” For the first time, they used brain scanning to determine that the high delayers showed greater activation in the prefrontal cortex while the low delayers had greater recruitment of the ventral striatum. This may reflect the differing use of of different “cold” and “hot” modes of cognition in choosing between competing impulses.

Anyway, I’m not going to go into great depth about the neuroscience here (as noted above, those who are interested can read the full paper freely). What caught my attention was the following quote in the press release:

“This is the first time we have located the specific brain areas related to delayed gratification. This could have major implications in the treatment of obesity and addictions,” says lead author Dr. B.J. Casey, director of the Sackler Institute for Developmental Psychobiology at Weill Cornell Medical College and the Sackler Professor of Developmental Psychobiology.

One of the interesting debates that I’ve become more attuned to in following the blogs of people like Yoni Freedhoff and Arya Sharma is the tendency to ascribe moral failings — a lack of willpower and unwillingness to make the “right” choices — to obese people. Dr. Sharma frequently argues that “Eat Less, Move More”-type advice is useless for losing weight, because it fails to understand the “countless ways in which the psychoneurobiology, energy physiology and metabolism in anyone who has lost weight” drive you to regain that weight.

So in this picture, does increased power of delayed gratification have any role in treating or avoiding obesity? Or are the biological imperatives too strong for anyone’s self-control? Dr. Sharma had a very interesting post a couple of weeks ago about the role of personal choice in weight loss, responding to a recent paper in the Journal of the American Dietetic Association. He doesn’t reject the role of impulse control in weight loss — in fact, he suggests it should be considered:

Recognising and fully acknowledging how the brain’s neural circuitry that underlies these behaviours interacts with (and is thus ultimately responsive to) environmental situations and cues can perhaps provide a far more realistic and effective counseling strategy.

Of course, losing weight and avoiding weight gain in the first place are two distinct questions — and in the long term, any success we have in tackling society’s growing levels of obesity will probably come from helping future generations avoid obesity in the first place. The Marshmallow Test data does tell us something interesting: that you can predict who’s most likely to become obese based on tests of brain function in pre-school. That has nothing to do with resting metabolic rate, aptitude for sports, or even what they’re being fed at home.

Obviously, this trait isn’t the root of the problem. Presumably humans have always been born with varying degrees of delayed gratification; it’s only in our modern society that low delayers are at risk of obesity. This is consistent with the idea of an “obesogenic environment” — a world with a copious oversupply of calorie-dense food, convenient labour-saving devices always available, ubiquitous advertising to tempt us into taking the first marshmallow.

But still… it suggests that choices matter. I realize this starts to sound like a moral judgement (i.e. obese people must have made the “wrong” choices), but I don’t mean it that way. In fact, the Marshmallow Test tells us these choices are, to some extent, hardwired into us. But by acknowledging the role of choices, and understanding how and why the “wrong” choices are made, perhaps we can increase our odds of making the right choices. Dr. Sharma suggests a few ways this might work in the post I quoted from above. Another option: the idea of “brain training” is in disrepute right now, partly because it was so dramatically overhyped and oversold a few years ago, but maybe it’s something to consider. It’s a topic that comes up (peripherally) in the Jockology column I just wrote for next Monday’s Globe, and I’m looking forward to seeing more research on it.

  1. Tamara
    September 1st, 2011 at 11:45 | #1

    Wow, this is fascinating stuff. As a child, I would have been a low delayer, no doubt. Gimme that marshmallow. But over the last two years, I have lost 50 pounds through running and what I have often considered ‘brain training’. I find your use of the word ‘choice’ in this piece apt, since the role of choice and making the right ones each day has been integral to my success. Thanks for this piece, I look forward to reading your column next week.

  2. Seth Leon
    September 1st, 2011 at 16:36 | #2

    Hi Alex,

    I have followed the marshmello study for years with interest. As you mention near the end of your post I think we should focus on whether this ‘trait’ to delay gratification is hardwired or if it can be learned/improved through practice.

    After all this one measure has demonstrated such profound influences on life outcomes multiple domains, and we do not even attempt to improve or teach this skill in our education system. I think it is an area ripe for research.

    I suspect that aerobic training (which we know can stimulate neurogenesis (hippocampus), increase heart rate variability, reduce stress etc…) would be an important area of this research. Of course there is the catch 22 that the better you are at delaying gratification the more succesful you may be in incorporating an aerobic regime.

    I also think meditation or mind/body practicies may also be useful but I am biased as a long time tai chi practioner/instructor.

    Thanks for the link

  3. Seth Leon
    September 7th, 2011 at 23:31 | #3

    Right on time here is some follow-up on this question.

    http://www.wired.com/wiredscience/frontal-cortex

    ‘But here’s the good news: Executive function can be significantly improved, especially if interventions begin at an early age. In the current issue of Science, Adele Diamond, a neuroscientist at the University of British Columbia, reviews the activities that can reliably boost these essential mental skills.

    The list is surprisingly varied, revolving around activities that are both engaging and challenging, such as computer exercises involving short-term memory, tae-kwon-do, yoga and difficult board games. Dr. Diamond also notes that certain school curricula, such as Montessori and Tools for the Mind, have also been shown to consistently increase executive function.’

  4. RH
    September 10th, 2011 at 10:13 | #4

    Marshmallows weren’t on sale in my country until recently, so I had my first when I was 20 something. Now I am the king of procrastination.

  1. September 2nd, 2011 at 15:59 | #1
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