Friday, May 27, 2011

Life isn't fair, and capitalism is making you fat

There's this blog that I've been reading for a long time (2 years or so?), and I've found it to be an excellent source of science-y information about food, nutrition, and biochemistry. The guy who writes it (Dr. Stephan Guyenet) has a PhD in neuroscience and currently studies the neurobiology of body fat regulation at the University of Washington. What attracted me to the blog in the first place was his ability to pick apart studies and look at what the results really said, as opposed to what was in the abstract or the study conclusion (surprisingly, not always the same thing). He's also really good at identifying assumption biases, particularly as they relate to study design.

Anyway. Dr. Guyenet is not actually a "paleo" eater but he's pretty paleo-friendly - I think he actually follows a more Weston A Price-type diet. Still, he has a lot of very interesting tidbits on his site and it's completely non-commercial (except for that one time where he was interested in the guy who ate nothing but potatoes for 2 months as a promotional stunt for the Washington Potato Growers Union).

His most recent series of posts is outlining his theory of why people carry more body fat than is necessary (beyond the meaningless "they eat too much" - if that were a useful explanation, obesity wouldn't be a problem - the question is WHY do they eat too much, unless you're Gary Taubes, in which case you just think they eat too much starch & sugar. Mr. Taubes still thinks "because they eat too much" is a crap explanation for obesity. It's a symptom, not a cause.)

Guyenet's theory, in a nutshell, says that people eat too much because modern food is too darned tasty, a lot of it tastes exactly the same every time you eat it, and it's available all the time. He postulates that the degree of "food reward" in a diet influences various mechanisms in the brain (leptin signalling among them) to raise the body's fat set-point (which is defined as the level of body fat that the body will defend by altering appetite) to take advantage of a recognized food surplus in order to store energy for later use. The key to this is that the brain uses "food reward" to determine food surplus - if there is a lot of tasty, satisfying food in the diet, the brain ramps up the appetite to take advantage of it. If the diet is bland and unrewarding, not so much - no matter how energy-dense the food is.

This worked very well in the past, when seasonal food variations meant that it was totally in your best interest to be able to override your normal appetite levels and stuff yourself silly for weeks on end when there were berries and fat little critters and easily accessible roots and whatnot, but that when you were down to the nasty bits of shredded dried meat and a few acorns in the back of the cave, it was a good idea to lose your appetite and live off your fat rather than eating the acorns too quickly, or burn yourself out trying to catch the last few skinny rabbits. Of course, back in the day, the stuff that hit the reward centres of the brain was the good, fresh, sweet & fatty stuff. Dried food (in the absence of things that make dried food delicious, like tamari sauce & maple syrup) is not so enjoyable to eat, requiring a lot of chewing for relatively little flavour, and stored nuts and tubers are just bland and filling. Fresh berries, or spring greens, or the livers and marrow of a freshly killed moose, on the other hand, are loaded with flavour, have interesting, easy-to-eat textures, and smell good. In other words, yum. This would even have worked for agrarian cultures, when fresh produce and newly-slaughtered animals would have produced a seasonal surplus that humans could use to bulk up, balanced by the late-winter fare of stored grains supplemented by whatever stored meat the technology could provide. Sugar and salt (both of which improve the taste of food and thus its reward value) have historically been precious commodities.

Humans aren't the only animals that store seasonal surpluses (or surpluses of any sort). Rats are opportunistic scavengers that also benefit from eating strategies that allow them to store fat against possible future scarcity. There are a lot of rat studies showing that you can make rats chubby by feeding them "supermarket food" (danishes, spam, oreos, etc.), whereas it's hard to make them fat on rat chow, even if the macronutrient ratios are the same. Yes, you read that right - the same percentages of fat, carbs & protein - but the rats will eat a lot more of it if it's tasty and has interesting textures. (Very little that resembles rat chow occurs in nature. Even the most disgusting-to-you potential rat food (bugs, human garbage) has objectively more flavour than rat chow.) You can produce a similar effect feeding two groups of rats the same stuff, only adding water to one group's food. The water makes the food taste better (to a rat) and they'll eat more of it and get fat. Humans are possibly a little more complex, and it's conceivable that other factors like sounds, ambient conditions, social aspects etc. have some influence on food reward. Also, humans rarely subsist on the human equivalent of rat chow - although one suspects that in the past, feeding prisoners gruel was a good call economy-wise not only because it was cheap, but because it actually worked to suppress prisoner appetites.

The other key to this theory is that the more similar a tasty food is to one that was eaten before, the more it tends to raise the set-point. This is because the brain learns to associate flavour (and probably texture & aural cues to some extent) with caloric intake, so tasty foods eaten repeatedly that taste the same each time are better at raising set-point than novel tasty foods. In other words, when you taste a new food, the brain says "better wait until we see what this does before we go nuts with it" but if it's one that's been eaten repeatedly with obvious caloric benefit, the brain goes all "dig in! eat as much as you can!" and loosens the reins on your appetite. (In other words, your brain knows damn well exactly how many calories are in that Big Mac and it's totally cool with that.) Non-tasty foods don't provide enough stimulation to trigger such a response, and completely flavourless foods seem to suppress appetite.

This whole theory makes some sense, and does explain why obesity rates have risen in the manner in which they have. Convenience foods - prepared foods you purchase, many of which are manufactured to be tasty rather than nutritious (ie, chips, cookies) - are a product of a market economy, and as such exist for only as long as consumers buy them. Industrial food manufacturers therefore engineer their food to provide as much "reward" as possible so they will be repurchased. (I heard on CBC's "Age of Persuasion" yesterday that Kellogs put a vast amount of money into concocting a unique "crunch" to outsell generic cornflakes.) Obesity rates closely mirror the availability and consumption of such foods. This also explains why the obesity rate in some traditional cultures skyrockets when people are exposed to western foods, even though the fat OR carb content remains the same or even decreases - because nearly all of the new foods (ie, shelf-stable & shippable to remoter locations) have been developed with palatability, not availability, in mind.

The obvious and unfortunate conclusion from this is that in order to obtain and maintain a desirable body fat percentage, far less delicious food is in your future - especially far less delicious "comfort food" that tastes the same every time - recipes with few ingredients in strictly controlled measure, packaged food (KD!) and fast food or even food from chain restaurants. Indeed, that's posited as the real reason that low-fat AND low-carb diets have some success, because initially, food reward is reduced on either, and eating processed food is typically reduced. These diets usually start to fail when dieters find ways to create the deliciousness to which they were previously accustomed within the boundaries of the diet (paleo brownies, yum! weight-watchers chocolate caramel pretzels!), which prompts their brains to go back to hungry-mode. (It should be noted, though, that a strict paleo diet limits fruits and sugars, even naturally occurring ones, on the grounds that these were not typically available year-round, and especially sugars (like honey) were hard to obtain and occasional, so a hard-core paleo diet would necessarily be lower in food reward values, so more likely to work long-term. Also more likely to result in some degree of social ostracization in the current food climate.)

This theory also suggests that stable and persistent fat loss, in a convenience-food environment, is going to be damned hard for individuals who are susceptible to excess food reward (in the same way that not everyone is susceptible to the pleasures of alcohol or crack cocaine). And, if you're one of those susceptible individuals (as I am) it's a sad thought that if you want to carry a healthy amount of fat, food is just not going to be as enjoyable or - importantly - such a reliable source of comfort. For the rest of your life. It's a good thing I never had any expectation of life being fair. On the other hand, it's probable that my extra flab is a good indicator that I've enjoyed food MORE than some other people up to now, so I guess it all evens out in the end, if this theory is correct.

There's actually a diet plan (more like a hack, but let's not quibble over terminology) that takes advantage of unflavoured food to reduce set-point easily. I'm experimenting with it now and I'll see how it goes. For the time being, the aforementioned blog post series is well worth reading.

Food Reward: A Dominant Factor In Obesity Part 1
Food Reward: A Dominant Factor In Obesity Part 2
Food Reward: A Dominant Factor In Obesity Part 3
Food Reward: A Dominant Factor In Obesity Part 4

There is also a podcast that is lengthy but worth listening to here.


Sunday, May 08, 2011

Unassailable Oatmeal

Yesterday I posted an interesting link on Facebook which detailed a study in Pediatrics done on a small (n=12) group of obese, adolescent boys. The study showed that eating an oatmeal breakfast (and, it should be noted, an oatmeal lunch) versus eating a vegetable-and-cheese omelette for both meals resulted in the boys consuming more calories after lunch, when they were permitted to eat as much as they like from a selection of foods. This was an interesting study because the results were partially opposite what proponents of whole grains have been maintaining (ie, that they provide fibre and bulk in the diet, which fills you up more and lets you eat less). I say partially because they actually had two oatmeal groups - one using instant oatmeal and one using a less-refined oatmeal, both with identical toppings, and indeed the less-processed oatmeal reduced subsequent food intake more. However, both oatmeals fared poorly compared with the omelettes. This study was a rarity in nutritional research in that it was experimental in design and very tightly controlled - far fewer potential confounds than in most other studies - AND it clearly measured actual intake and actual blood glucose levels rather than reported intake and/or hunger. What I find even more interesting is that while spikes & dips in blood glucose as a result of eating cereals and other high-GI foods are pretty well-acknowledged in nutritional research, the effect of those spikes & dips on later food intake has not been so well-documented.

I apparently have a lot of friends who maintain that oatmeal is an awesome breakfast, and indeed, I was formerly a huge fan of the oatmeal, too. Easy to prepare, hot, filling, and, with a modest amount of brown sugar and maybe some raisins or other dried fruit, satisfyingly delicious. Especially the steel-cut oats. Yum. (Critics please note that I am not disputing oatmeal's yumminess. Of all the grains, it ranks second in my book only to barley for inherent deliciousness.) But I was unprepared for the angry backlash when I questioned the overall health-providing aura of the Oatmeal. It was like posting a link claiming Elizabeth May used to work for Monsanto. OMG HOW COULD YOU SAY THAT?!?!?!?! (Later clarified to "Who are you to tell me what to eat, internet nutrition sucks, everyone is an individual and *I* am very cool with oatmeal" - which are fair points, but worth looking at more closely.)

Being yummy and filling is not the same as being good for you. And just because something is FILLING doesn't mean that you'll eat less, later. If you eat oatmeal for brekkie, can you then be fine *all afternoon* if you have only a salad and a couple hard-boiled eggs for lunch? Is an afternoon snack a necessity? Now, you may feel hungry earlier towards lunchtime if you eat protein and veggies for breakfast rather than oatmeal (hard to say if this is due to faster absorption of nutrients, response to an unexpected LACK of blood glucose spike, or stretched-out tummy, or even true), but hunger levels do not necessarily dictate later appetite. I'm sure everyone has had times when they've been hungry, but were satisfied by fairly little food, and conversely sat down to dinner really not so hungry but then scarfed an 8-oz steak, baked potato with butter, and 3 helpings of cheesy broccoli anyhow. In other words, hunger isn't what we're looking at, we're looking at post-oatmeal eating. Different.

Interestingly, few if any of the Facebook oatmeal-defenders are overweight. (Massively pregnant sisters don't really count.) And as the discussion on Facebook pointed out, eating more later is not necessarily a bad thing. If you're an athlete, or if you work a physically demanding job, or your personality and food habits are such that you have a tendency to forget to eat, then you may very well want to eat a breakfast that enhances your appetite later on. This study was not aimed at providing useful information for people like this. It was aimed at people who have weight to lose, and who want to be able to decrease their overall caloric intake. Is it such a stretch to say that people like that, who are eating oatmeal for breakfast, should probably take a week or two and try something different?

The pro-oatmeal crowd kept prodding, though, and because I am ornery and a fully brainwashed paleophile I posted a link describing an old, old study showing that a single variable - oatmeal - in an adequately controlled experimental setting could account for a significant portion of dental caries in children. The reason it's an old, old study is that handy orphanages with piles of kids on which you can experiment like that don't really exist anymore. But the researchers were able to clearly show that oatmeal intake was positively associated with development of caries (cavities). Oh noes! Not the oatmeal, doing something BAD!!!! Well yeah. That particular result was most likely due to the phytate content of oatmeal, and it is possible to get around that one, but your oatmeal won't taste the same. (I like it a little sour, but I can see how that's a bit of a tough sell.)

So, two experimental studies show that oatmeal may not be the perfect breakfast food. Why get upset about that?

I think part of it is that people are sick to death of hearing that foods that were supposedly good for you aren't a panacea of healthy, or that previously "bad" stuff that was pretty easy to avoid (liver, anyone?) is actually really, really good for you and you should eat lots of it. Food ought to make us feel good. It's damned hard to feel good about eating when some nutrition dilettante tries to tell you that dear old oatmeal, which is one of the few foods that has enjoyed a good nutritional reputation since Roman times, MIGHT not be so good. If we can question oatmeal, for chrissakes, is ANYTHING sacred? (And at what point do I get labeled an orthorexic?)

The real question underlying this is, does it do us more harm than good to put our considerable, but still very flawed, scientific know-how into examining what we eat? Many good food writers (Michael Pollan among them) have noted the absence of a real "food culture" in North American society. Much of our angst about food and probably no small number of diet-related disorders is driven by sheer uncertainty about what we should eat. And it's easy to answer the "should we listen to research scientists?" with a quick "No!" because intuitively, we know that if we can stick with traditional foods - like oatmeal - that we've eaten for hundreds of years, we're good, right? Granny ate oatmeal every day and lived to be 107, etc.

Except, what if Granny *could* have lived to be 112, and maybe not had chronic hemorrhoids for the last 20 years of her life? What Granny carried a series of fortunate genes and a gutfull of awesome bacteria gleaned by accident or as a result of a borderline-unhealthy childhood obsession with being a chicken? Is her oatmeal still good for you?

See, science helps with these questions - but it doesn't answer them definitively. Science is, by its nature, always changing in its body of knowledge. As more experiments are done, more epidemiological data analyzed, and more evolutionary puzzles unraveled, our knowledge base changes, and our ideas about optimal or even healthy nutrition change. And, too, science has a human element, and human interests and even hubris can take over a whole field and distort its findings for decades through unnoticed confirmation bias, unexamined assumptions and statistical trickery for funding purposes. Nutritional science is also incredibly difficult to do WELL because we have all these inconvenient rules about experimenting on humans, and while rats and mice are convenient, they're different from us in some pretty important ways. So, it's easy to dismiss nutritional science as next to useless, and on more than one occasion I've done so too.

But if we're going to dismiss (or severely limit) direct science (ie, reading research articles) as a factor in deciding what to eat (or what not to eat), I think we also need to look really hard at what DOES influence what we eat. Government policy? Media? Advertising? Family traditions? Religious traditions? Packaging? Grocery store placement? Simple palatability? The limits of our culinary skill? Time? Is using these as rationale for what you put in your body really any better than using ever-changing scientific research findings? (It's entirely possible that it makes you a less annoying person, I'll grant that.) And if you prefer to rely on medical professionals for your dietary advice, do you ever actually ask how much training your doctor/nurse/nutritionist received, how many journals he/she subscribes to and what was the last interesting article he/she read that made him/her revise his/her views on whatever?

And does it really hurt to examine your food periodically, and ask if it's doing enough for you?

All right oatmeal fans, comments are all yours. Go for it. Justify your love for the oatmeal. Rip apart the internet nutrition, convince me I'm a loser nutrition geek who ought to have better things to do with her Sunday afternoons...