I just got a fascinating paper from the business and marketing literature describing studies done on how people’s consumption increases when they believe the foods they are eating are low-fat. The paper, published in the Journal of Marketing Research, describes three studies showing that subjects, particularly if they are overweight, tend to overeat snack foods when they believe they are lower in fat.
In the first study, the researchers provided the subjects–who were students and their families visiting a university open house–with gallon containers of unusual colored M&Ms labeled either ‘New Colors of Regular M&Ms’ or ‘New Low-fat M&Ms.” (The M&Ms were exactly the same–there are no low-fat M&Ms. The only difference in these M&Ms was the labels on the bowls.) The subjects were instructed to eat as much as they wanted as they roamed through the display areas. Upon leaving, the subjects gave up their containers of candy and answered a questionnaire. The researchers measured the amount of M&Ms left in the bowls and compared the consumption of the ‘Regular’ to the ‘Low-fat’ and correlated the results to the answers on the questionnaire.
It turns out that the people eating the ‘low-fat’ M&Ms consumed 28.4% more calories than those consuming the ‘regular’ M&Ms. When broken down by weight of the subjects, the differences were even more dramatic.
Overweight subjects eating the ‘low-fat’ M&Ms consumed 47% more calories than than did overweight subjects who got the ‘regular’ M&Ms. Normal weight subjects consumed only 16% more calories than the normal weight subjects eating the ‘regular’ M&Ms.
All subjects were asked to estimate how many calories of M&Ms they had eaten. All subjects significantly underestimated their consumption, but the overweight subjects way underestimated how many of the ‘low-fat’ M&Ms they had eaten.
These findings are not just fascinating, they have real world implications. As the authors point out:

Because low-fat foods are believed to contain fewer calories than regular versions, it might be reasonable for a hungry calorie counter to consume more candy when it is described as low-fat than when it is not. The key question for public health is whether a low-fat claim would lead such a person to eat so much more that it offsets the potentially lower-calorie density of low-fat foods. To determine this, we surveyed the fat and calorie content of all brands of chocolate candies, bars, cookies, milk drinks, and muffins with a least a 5% market share.
We found 17 brands that were sold with both a regular and a low-fat version of the same product. The serving sizes indicated on the products were similar for both versions. Although, on average, the low-fat versions contained 59% less fat per serving than regular versions, they contained only 15% fewer calories(140 verses 170 calories). If participants in [the study] had eaten real low-fat M&Ms (with the market average of 15% fewer calories than regular chocolate candies), they would have consumed 47% less fat but 9% more total calories. This is a conservative estimate. In reality, the increase in calories is likely to be even higher because the ingredients used to replace fat tend to make people hungrier. [My italics]

What is it, do you suppose, that they use to replace the fat in low-fat candies that makes people hungrier? You got it. Sugar. And nowadays probably high-fructose corn syrup.
So, we’ve got a situation where people think they’re being good and eating less fat, but in reality are consuming at least 9% more calories than they would had they eaten the non-low-fat variety. And chowing down on way, way more sugar than that found in the regular varieties of snacks. Knowing, as all good low-carbers do, the profound effects of sugar on fat-storing metabolism, it’s fairly easy to see why low-fat foods would lead to obesity.
These foods encourage people to eat more sugar.
I’ll post on the other two studies described in this paper over the next couple of days. It’s fascinating stuff.


  1. Mike–do you think Americans in reality are eating less fat than they used to? Most people I know think they should eat less fat but go on eating whatever they want. My own thought is that total fat intake, over the last few decades, has remained about the same, but people overall are eating less saturated fat, much more vegetable oil (hydrogenated and otherwise), more starch and sugar, and more calories–with predictable results.
    Hi Paul–
    Based on the fairly considerable research I’ve done on the subject, you’re pretty much correct.  There has been a little drop off in overall fat consumption, but not much.  Saturated fat consumption has dropped pretty markedly, but vegetable oil consumption is up.  Overall caloric intake is up as well with virtually all of the increased calories coming in as carbohydrates.  With the increase in carbohydrate intake and the slight drop off in fat intake, it has made fat intake as a percentage of calories drop from about 45% in the 1970s to about 34% today.
    Hope this answers your question.

  2. Based on the investing strategy of ” if they’re that bloody stupid, then the hell with them…”, perhaps one should considering adding M&M’s to the stock portfolio that already contains the RJ Reynold’s stock.
    Hello James–
    Good idea.  I’ll look into it.

  3. This is so interesting. It just shows how people can be unconcious eaters. I, as a low carber, am still careful when eating low carb goodies. If I have a pack of low carb ( sugarfree ) M&Ms, I would only eat a small amount. Hey, tomorrow is another day, right? Thankfully, I am able to control my sugar appetite by avoiding sugar in the first place.
    Hi Mary–
    Indeed. The author of this paper has a popular book out about his research called Mindless Eating. I just finished it, and let me tell you, it’s fascinating. People eat mindlessly constanty. Anyone reading this book will understand why we have an obesity epidemic.

  4. This is no surprise at all to those of us who feel ravenous on a low-fat diet, or even a so-called “balanced” diet that includes starches and sugars. I can recall many times eating a rather hefty meal, and within an hour, feeling like I was starving again.
    I’ve recently discovered that (for me) even eating too many moderately low carb vegetables can also lead to that ravenously-hungry-within-an-hour-or-two feeling. I really have to watch my portions on things like broccoli and cauliflower.
    Most people aren’t that sensitive to carbs, obviously. Guess I’m just lucky like that. 😉
    Hi Calianna–
    It’s called the Chinese-restaurant syndrome.  Eat a big meal of mainly veggies and you’re hungry again in an hour.  Add some good quality fat and protein, and it’s a long time until you’re hungry again.  If it’s mainly fat and protein, it’s a long, long time before you think about eating.

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