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food rewardBy Joey Lott

There are a few of us who have done so many stupid food restriction hijinks that our main concern is “how can I put on some weight and keep it?” But by and large (pun intended) the overwhelming majority of people today are nearly obsessed with weight loss. The idea that there is an obesity epidemic is virtually unchallenged, and to be sure, the statistics are damning. We’re getting fatter. With the single exception of sub-Saharan Africa everyone – man, woman, and child – seems to be getting fatter worldwide. But why? And is it necessarily a problem?

In a recent post here on 180D the “food reward hypothesis of obesity”, or what I’ll just call the food reward theory, was briefly mentioned. I was familiar with the theory, having read Stephan Guyenet’s blog fairly extensively over the years. (Guyenet is one of the leading advocates of the theory as what he terms “the dominant factor in obesity”.) Guyenet’s views on the importance of the theory are pretty bold. But I didn’t recall ever being won over by his arguments.

This recent mention on 180D (and a challenge to my view that it’s not a very convincing theory for broad application) caused me to revisit the theory. I relied, once again, on Guyenet’s arguments and references to explain the theory to me. I want to share with you what I have learned and my critique.

Before we go on, though, I should warn you that I do have biases. I am not married to my biases. I am always open to evidence that counters my biases. After all, the true spirit of science is to always challenge theories and biases, attempting to prove them wrong. But even though I don’t believe my biases to be the absolute truth, I feel that I should share them with you up front so that you know where I am coming from.

Although there is great talk about a so-called “obesity epidemic”, I am skeptical of much of the hysteria. Yes, the evidence is pretty damn clear. With the singular exception of sub-Saharan Africa, we all are getting fatter. And yes, there is a definite increase in the cases of many diseases like type 2 diabetes, cardiovascular disease, and various types of cancer. And yes, there is some correlation between fatness and some diseases. I’m not denying that. In fact, I’m not denying anything.

However, I am, as I said, skeptical of the hysteria. Not because there might not be something to be concerned about. But rather, because hysteria doesn’t tend to produce very good science or honest investigations of matters. Instead it’s, “Give us the simple answer now so we can go back to the football game!”

I detail much of my investigation in this matter in my forthcoming book titled (provocatively), Big Fat Lies. You can get it for free when it comes out HERE. The actual book isn’t nearly as provocative as the title. Instead, it’s a fairly level-headed examination of whether or not the supposed causal connections between fat and disease is necessarily what we’ve been led to believe. I won’t go into all the details here, but suffice it to say, fatness (particularly moderate amounts of fat) doesn’t always (or even all that often) clearly cause disease. And it is certainly possible that both fatness and disease are sometimes the symptoms of the same causes. And, incidentally, one possible contributor to both fatness and increases in disease rates is a population that is increasingly aging (and having babies at older ages too which, by the way, predisposes the child to be fatter). So an aging population may be the exclamation mark that screams “epidemic”, accentuating some trends that can also partially be explained by increasing use of pharmaceutical drugs, increasing sleep debt, and increasing stress, among other things. Food reward probably plays a role too, by the way. I am just not yet certain how much and whether or not the proposed “solutions” are appropriate or even safe.

So that’s one bias.

I’m also particularly sensitive to the dangers of anything being misunderstood or appropriated to fuel unhealthy food obsessions and restrictions. As most of us who are regular readers of 180D know all too well, that’s a slippery slope, and it leads directly to hell. As Matt mentioned in a comment recently, advocating for restriction will likely help a very small number of people while leading the overwhelming majority into a nightmare of food restriction. So I am extremely cautious about advocating for anything that is restrictive. (Though it’s awfully easy to make that mistake even in subtle ways, and I have done that more often than I’d like.)

So there you have my biases. At least the relevant ones of which I am aware at the moment. Let’s continue.

The food reward theory, as Guyenet defines it, “states that the reward (reinforcing, motivational) and hedonic (pleasure, palatability) value of food influence food intake and body fatness, contributing to the development of obesity.“

Food reward may not affect everyone equally – even according to the proponents of the theory. Not just because some people have greater will power and abstain from all that horribly, deliciously addictive stuff. But rather, because some people may be conditioned or just genetically predisposed to be susceptible.

So in general, I think most people will agree both from their own personal experience and from a review of the relevant scientific literature that it is a reasonable theory. Lays and Coca-Cola employ food scientists to increase food reward and palatability to increase repeat sales. And studies do show that altering various factors to increase reward and/or palatability will increase caloric intake by most humans in the short term.

But my argument is that there is not yet evidence to confirm that food reward or palatability works long term for all or even most humans to increase caloric intake beyond actual needs and contribute to fat gain. Or, really, I should be more specific. It’s not even the fat gain that’s the issue. It’s the health problems. I’m not convinced that there is yet a strong case to be made that foods that are designed so that “bet you can’t eat just one” can be explained as, as Guyenet states, “the dominant factor in obesity” (where obesity is imagined to mean not just fatness, but also health problems).

As we’ll see, the research that Guyenet* cites on the matter actually suggests that the long term fattening effect of rewarding/palatable foods affect only susceptible people. And as Matt pointed out in the comments of the previous post, one likely factor that can contribute to susceptibility to the fattening effects of rewarding/palatable foods is restriction. So ironically, many people may potentially (this is not confirmed, of course) make themselves susceptible to the negative effects of such foods by denying themselves their physical/dietary needs and restricting/dieting to extremes. Sure, it’s hard to argue that Coca-Cola is a necessary food. But many of us know all too well the pattern of restricting not only Coca-Cola and Doritos, but also all sugar and all fried and salty foods. Then, heck, why not restrict all carbohydrates too? And all dairy. And anything with any taste or calories whatsoever. Then, when the breaking point is reached, a binge on all the “forbidden” foods is common. Plus, the yo-yo of caloric restriction is pretty well known to increase fat gain long term and, more importantly, contribute to metabolic derangement and health problems.

* Incidentally, if you aren’t familiar with Guyenet’s blog, Whole Health Source, you might want to check it out. I have a lot of respect for Guyenet’s work. He has done a great deal to point out the fallacy of low carbohydrate doctrine, and I suspect he has saved many low carbohydrate dieters from further destroying their health. And his work on the food reward theory, even though I don’t happen to find the argument as convincing as others do, is quite good too and worth checking out.

Specifically in defense of the food reward theory Guyenet references a bunch of studies and then writes, “Even if not all of the studies are perfect, at some point, one has to acknowledge that there are a lot of mutually buttressing lines of evidence here. “ In other words, there are lots of pieces there that if one looks at all of them Guyenet believes a picture of the food reward theory (as the “dominant factor in obesity”) should emerge. I just haven’t yet seen that picture emerge so clearly.

Incidentally, for those interested in further reading on the subject, Guyenet has several excellent series of posts that elaborate on why he believes that food reward is the “dominant factor in obesity”. See the start of those series here and here.

What is troublesome about the theory is that at his best, Guyenet, one of the leading proponents of the theory, does not produce a convincing argument. I looked at every abstract he references in his posts specific to food reward. Yes, I know that he admits that the individual studies aren’t perfect. (Who is?) That’s okay by me. But in my view there’s a difference between imperfect and…how to put this…Let’s just say, I was wondering, “Where’s the beef?”

A lot of the studies he cites are non-human studies. Apart from the ethical concerns (which is a whole other topic), I have read far too many bogus conclusions about human health that were based on rat studies. In rats it was solid. Feed rats high fructose corn syrup, their waistlines blow up like the Goodyear blimp. So it’s a done deal, right? In humans surely the same is true. Whoops. Not so fast. Turns out it doesn’t work that way. Or how ‘bout this. Feed rats a little bit of fructose and “Whoa!” their livers turn into fatty goo. So it must be the same in humans, right? Wrong again. Damn! How frustrating!

So I’m extremely skeptical of non-human feeding studies. Not only do rats have different metabolisms, but lab rats are…get this…caged and often subjected to lots of stress. And a lot of the time the logic in rat studies is just plain weird. For example, and I’m not making this up, some studies have done the following. They take a group of rats and withhold sugar water for 12 hours a day. During the first hour when the rats are reintroduced to the sugar water they binge on it before eating rat chow. The conclusion? “Holy shit! Sugar is more addictive than cocaine!”

“Exsqueeze me?”

But what about the human studies? Well, it may not surprise you, but I’m not so won over by what Guyenet presents in this regard. Here are some examples.

Effect of altering the variety of sensorially distinct foods, of the same macronutrient content, on food intake and body weight in men.

Get together a group of men. Give them foods that are all nutritionally identical but that look different. Men eat more calories when there are more “sensorially distinct” (yet nutritionally identical) foods.

Palatability affects satiation but not satiety.

Get together a group of people and feed them tomato soup. Some of the tomato soup is just what you’d expect it to be and probably tastes fairly decent. But some of the people got tomato soup with varying amounts of citric acid. Surprise! The more citric acid, the less people ate. Yet all people felt more or less equally satisfied (called satiation) after eating however much they ate. And when given a buffet style meal afterward, all people at equal amounts, so in total, those who ate the less pleasant soup ate less.

The takeaway? Make food less palatable and people may eat less during a single meal in a controlled setting.

Effects of changes in palatability on food intake and the cumulative food intake curve in man.

Add cumin to yogurt. Some people don’t like the taste. Those who don’t like the taste will eat less than those who like the taste.

I could have told you that!

The relative reinforcing value of food predicts weight gain in a longitudinal study of 7–10-y-old children.

Get together a group of kids. Tell the kids that they can either have a food reward or a non food reward for completing a certain number of tasks. With each reward issued, increase the number tasks necessary to earn a food reward but keep the number of tasks necessary for a non food reward stable. Maximum number of tasks for nonfood is 20. Maximum number of tasks for food is 240. So at the end, kids have to really want the food to work toward it.

Some kids (about 3 percent) will go for low hanging fruit and ask for the non food reward each time. Some kids (about 3 percent) will go for the food reward every time, despite the increasing difficulty. The rest of the kids are somewhere in between.

A year later follow up with the kids. Measure and weigh them and see if their BMIs have changed and if the number of food rewards chosen was a predictor of BMI increase.

No dice.

Follow up again still another year later. Same deal. This time? “Jackpot!” The kids who worked harder for food rewards were gaining weight faster than the kids who didn’t want the food rewards so much.

Right. So the takeaway is that maybe some kids who really want food a lot will get fatter than kids who don’t really care so much.

Many of the other studies that Guyenet references show that alterations in dopamine signaling may predict susceptibility to food reward. So, for example, one person has “normal” dopamine stuff happening, and so that person can probably be surrounded by Doritos and Big Macs all day every day and probably not be greatly influenced. But another person may have different dopamine stuff going on. And if that person lives in a macrobiotic cult in the Alaskan wilderness far from any McDonald’s, he’ll stay lean (probably too lean). But drop that person in the middle of most American grocery stores and it’ll be “nom, nom, nom, nom, can’t stop, can’t stop devouring Cheetos even though my sides are splitting.”

But the thing that remains unclear is how frequently this is actually a problem. What percentage of fat people have the dopamine stuff going on as noted in these studies? It could be 100 percent, of course. But then again, it might be 1 percent or less. So based on these studies we could say that food reward could be a major, perhaps the causal factor in fat gain and perhaps even health problems among some as of yet undetermined percentage of the population. And that could be a very important piece of information that could help a lot of people. (Because chronic, painful bingeing isn’t very fun.) But we just don’t know what the significance of this finding is.

That’s my summary of my findings thus far. I promise you, I didn’t cherry pick these studies to shine an unfavorable light on the theory. Actually, I cherry picked these studies because they are the ones that seemed most relevant.

My main concern about promoting the food reward theory as the “dominant factor” in increased fatness is that it isn’t (in my view) proven, and it can easily lead to disordered eating with all the negative health consequences that typically follow. Promoting a diet that has low palatability (i.e. “clean eating”) as something that people who feel themselves to be “overweight” should do is, in my view, potentially dangerous.

Here’s why. First of all, if someone’s weight is increased because of preconception parental health, pharmaceutical drug use, sleep debt, or a history of dieting/restriction, making food less palatable (“clean eating”) can simply fuel unhealthy food obsession and unintentional calorie restriction. Many of us have experiences variations on this, and we know that it ain’t pretty.

For another thing, if someone really is fat because they are susceptible to food reward, “eating clean” probably won’t make that person less susceptible. Instead, if dopamine signaling stuff can make one susceptible to food reward so that such a person truly feels powerless to stop eating Twinkies and Doritos even after he or she is incredibly uncomfortable (by the way, been there, done that for years when I was younger…I know how horrible that can be), then it would be worthwhile to find ways to change the dopamine signaling so that a person can still feel pleasure yet also be able to eat to satiety and stop. But “eating clean” may not be the best solution.

While the food reward theory isn’t inherently fat shaming – not at all – I see that it can easily be turned into just another tool to shame people for being fat. It can turn into, “You fatty fatterson there, how dare you eat that palatable food. You should be eating brown rice instead.”

It seems to me that there’s a lot more to learn about all of this. And meanwhile, I am cautious about any recommendations that are likely to be harmful to the majority and only possibly helpful to a few.

About the Author

Joey Lott author picJoey Lott is health researcher and a more than 10-time Amazon bestselling author. Get his future health books for free, including his upcoming title Big Fat Lies at www.joeylotthealth.com. Read more of Joey’s work in his books.