2.14.2008

sweet thoughts on valentine's day

My first job was at a fast-food restaurant in a mall (a certain chain specializing in chicken that is only open 6 days/week). There was a phenomenon that I first noticed on that job that, though I did not appreciate its significance at the time, I have since come to believe is instructive.

It goes something like this: a customer of some—shall we say, considerable carriage--comes up to the counter. He or she orders a fried chicken sandwich or two, often with cheese, a large order of fries, a cup of cole slaw (~30% mayonnaise by volume), and a 32-oz—wait for it--diet soda.

Now, far be it from me to extol the virtues of high-fructose corn syrup, the consumption of which (in quantity) has been linked to elevated levels of ureic acid in the blood which definitely leads to kidney stones and may (there is mounting evidence) be linked to cardiovascular disease. (All of this is in addition to the problems associated with consuming such concentrated calories in the form of simple carbohydrates; i.e., elevated blood sugar, insulin resistance, and weight gain.) However, even if you assume that our corpulent customer is making a one-to-one substitution of diet soda for leaded—and I’m not sure we should assume that; more on that below--the caloric savings is clearly not enough of an offset to make a difference. S/he’s still fat.

Now I realize I’ve given you an anecdote here, and that you have to trust me (and my memory some 14 years out) when I say that this customer was not exceptional but in fact typical—an overweight customer eating a large amount of food and washing it down with diet soda. And even if I had hard data to support my more general assertion that the habitual consumer of diet soda is, on average, overweight to obese, you could still argue that this is a matter of which comes first: the (deep-fried) chicken or the (4-)egg (Denver omelet)? More to the point, do people drink diet soda because they’re fat (and don’t want to be), or is the diet soda making/keeping them fat?

While the first option is appealing in its simplicity, I think that the second bears careful consideration. So, too, do the authors of an upcoming paper in Behavioral Neuroscience discussed briefly by Art de Vany here.

The rats who ate artificially sweetened yogurt consumed more food overall and gained more weight. The body temperatures of those rats also didn’t rise as high as the others. “That might be a kind of measure of energy expenditure, suggesting not only are the animals eating more calories, they may be expending or burning up fewer calories,” Swithers said.


I haven’t been able to pull up the paper yet [Ed.--here it is], but as Dr. de Vany points out, this sounds like artificial sweetener may be tricking out the satiety centers of the hypothalamus, causing a release of insulin in advance of a blood glucose spike that doesn’t come…with the net effect of causing blood sugar to fall precipitously, stimulating hunger. Couple that to a change in thermoregulation (which may or may not be directly related, but in the rats certainly seems to be happening) and you are set up for weight gain.

My personal prejudice is that I am against “fake food” in all its forms. I won’t eat anything with artificial sweetener in it on purpose—not only because I think these are chemicals for which we have absolutely no metabolic adaptations, but because they taste awful. Reduced fat dairy is OK for cooking some things—even though I generally hate it—as long as there is nothing synthetic put in to “replace” the fat. Don’t even get me started on soy products—after trying out soy milk a few years ago, I found myself with an odd craving for the stuff and eventually developed what I am 90% certain is a mild allergy to it, and only “mild” because I quit drinking it the moment I made the connection.

But beyond all of that, I have generally found that “diet food” is tremendously unsatisfying, I think in no small part because it contains less of the natural components of food (protein, fat, sugar) that signal to your brain that you have eaten. My guess is that people tend to eat more of it, or just more of everything, as a result. However, if this study translates to humans at all, the situation might be much, much worse than that.

I also wonder the extent to which this may be related to the phenomenon that many people report upon reducing the amount of sugar and starch in their diet; namely, the less of it you consume, the more you lose your taste for it. I can definitely vouch for this—I almost never drink soda any more, and generally regret it if I do. I find orange and other fruit juices unbearably sweet. I’m pretty much done with pasta. The only candy I like is chocolate—the more bitter, the better. [m], who bakes all the time, is constantly cutting the sugar down (not replacing it) in her recipes, and we both tend to like the result much better than if she’d followed the recipe exactly. If instead of reducing sugar in your diet, you are replacing it with a hyper-sweet synthetic, you probably aren’t benefiting from losing your taste for sugar.

The take-home message here, as far as I am concerned, is ditch the fake food. Eat well…and less.

8 comments:

Marsosudiro said...

Swear to God, I like drinking Diet Coke just for the moderately bitter taste. (Same goes for light beer which I like even better.)

That said, I *may* be discovering a substitute with carbonated mineral water. It has enough flavor to go against food (without giving me the nasty sensation of a diluted meal washing around my mouth).

Oh and by the way -- I weight about ten pounds more than I'd like :-)

Gino said...

i started drinking diet soda when i was 19, and about 35lbs lighter than i am now. ok,so now i'm near on 44, so i think the extra 25yrs and 35lbs are a natural phenom of a dude getting older, as opposed to drinking the wrong thing.

but, like you, i oppose fake food.
it was a taste issue, plain and simple.

your thoughts appear to have some merit. just look around.
my mom-in-law wieghed like 400+lbs, and only 5'4".
everything in that house was fat free,sugar-free, taste-free.
i hated going over there because you could never get a decent meal.

rob said...

I am also a fan of the Diet Coke/Pepsi. More than anything, however, it is a substrate to provide the caffeine that I need, as I am not a coffee drinker. More curiously, however, why is chik-fil-a only open 6 days a week? Do they take Mondays off like barbers?

Brian said...

Hey, far be it from me to come between a man and the beverage of his choosing...

Chick-fil-a is closed on Sundays because its founder is a devout Baptist.

RW said...

I'm glad I'm not the only person who has been amused by the "and a diet coke" order to sort of placate the grease and slime or something.

Never fear, when I go to the deli and order salami I automatically say "the kind that's bad for you" (and everybody laughs from recognition) when they ask if I want to fat free.

Arthur said...

Keep in mind that rats have brown fat/adipose tissue and humans lack this heat generator. Many observations of increased energy expenditure in rats (sometimes due to thermogenesis) does not manifest itself in humans under the same conditions.

That said, I am more of the opinion that humans who drink diet soda have other behaviors associated with metabolic disease that are likely to lead to CV risk later in life. I'm sure diet soda does contribute, but not to the extent that has been sensationalized in the news.

Brian said...

Thanks for the comment, A. Good to hear from you.

So do you know if the rat vs. human issue re: adipose tissue and thermogenesis cuts both ways, i.e., reports of decreased energy expenditure also don't translate from rats to humans?

I have since had a chance to read through the paper (quickly)...the basic framework is Pavlovian conditioning (sweetness is a cue for anticipated caloric intake--artificial sweeteners uncouple this). They don't really get into physiology, except in the discussion, and they point out that the change in body temperature may or may not be part of the altered "cephalic phase reflex" (a new term to me).

The changes in weight and food consumption are pretty compelling.

Naturally the human situation is much more complex; but I am becoming increasingly convinced that weight gain and metabolic syndrome are not simple functions of thermodynamics.

Arthur said...

Chuck told me a while ago, and I have since come across uncoupling proteins that make the mitochondrial membrane more porous, requiring additional ATP to keep the proton pumps running to maintain the ionic gradient.

By burning more ATP, the cell consumes more energy/glucose.

Of course, this is what brown fat does in rodents.

Yes, metabolic syndrome is a hugely complex and not a simple issue of thermodynamics.

But, if pharm companies are willing to research drugs that mess with mitochondria and people are willing to take them rather than change their diet and exercise, well, then I'm not going to argue with affecting thermogenesis as a means to treat diabetes.

As for translating decreased energy expenditure in rats to humans, I think it translates very well. I believe sedentary/slow metabolism rodents eating a high calorie diet are the typical animal model for diabetes.