mathbabe

I recently finished a book that made rethink being fat, and the cause of the worldwide “obesity epidemic”. Rethink in a good way.

Namely, it suggested the following possibility. What if, rather than getting fat because we are overeating, we overeat because we are getting fat? Another way of thinking about this is that there’s something going on that makes us both store fat away and overeat – that they are both symptomatic of some other problem.

In particular, this would imply that the fact of being fat is not a moral weakness, not a mere lack of willpower. Since I long ago dismissed the willpower hypothesis myself (I don’t seem to have trouble with other aspects of my life which require planning and willpower, why do I have so much trouble with this even though I’ve seriously tried?), this idea comes as something of a “duh” moment, but a welcome one.

To get in the appropriate mindset for this idea, think for a moment about all of the studies you hear about feeding animals such as rats, rabbits, monkeys, pigs, etc. different diets, and noting that sometimes the diet makes them super fat, and sometimes it doesn’t. Sometimes the animals are bred to have a genetic defect, or a pituitary or other gland is removed, and that has an effect on their fatness as well. In other words, there’s some kind of internal chemical thing going on with these animals which causes this condition.

Bottomline: we never accuse the fat mice of lacking will power.

So what is this thing that causes overeating and fat accumulation? The theory given in the book is as follows.

Fat cells are active little chemical warehouses which accept fat molecules and allow fat molecules to leave in two separate (but not unrelated) processes. Rather than thinking of fat as being stored there until the moment it is needed, instead think of the flow of fat molecules both into and out of each fat cell as two constant processes, so it’s actually better to consider the rate of those flows, the inward rate and the outward rate.

Suppose the outward rate of the fat molecules is somehow suppressed compared to the inward rate. So the fat molecules are being allowed into the fat cells just fine but they aren’t leaving the fat cells easily. What would happen?

In the short term, this would happen: lacking the appropriate amount of energy, the overall system would feel internally starved and get super hungry and quickly cause the animal to overeat to compensate for the lack of available energy.

In the longer term, the number of fat cells (or maybe the size of the average fat cell) would increase until the energy flow is sufficient to satisfy the internal needs of the system. In other words, the animal would gain a certain amount of weight (in the form of fat) and stay there, once the internal equilibrium is reached. This jives with the fact that people seem to have a certain “set point” of weight, including overweight. Indeed the amount of fat an animal has in equilibrium allows us to estimate how suppressed the outward flow of energy is.

What causes this suppressed outward rate? The book suggests that it’s elevated insulin. And what causes chronic elevated insulin? The book suggests that the main culprit is refined carbohydrates.

In particular, the author, Gary Taubes, suggests that by avoiding refined carbohydrates such as flour, sugar, and corn syrup, we can bring our insulin levels down to reasonable levels and the outward rate of fat from fat cells will no longer be suppressed.

Not everyone reacts in exactly the same way to refined carbs (i.e. not all insulin responses are identical) and scaled definitely matters, so eating 180 pounds of sugar a year is worse than 90 pounds a year, according to the theory. Moreover, things get progressively worse over time and it takes about 20 years of carb overloading to have such effects.

It’s easier said than done to avoid such foods as an individual living in our culture (nothing at Starbucks, nothing at a newsstand, almost nothing at a bodega), but one thing I like about this theory is that it actually explains the obesity epidemic pretty well: as the author points out, massively scaled refined carbohydrates have only been consumed at such rates for a short while, and the correlations with weight gain are pretty high.

Moreover, and I know this from personally avoiding most carbs for the past 6 months (which I started doing for another, related reason – I hadn’t read the book yet!). I’ve lost weight easily, and I haven’t ever been hungry, even compared to what I used to experience when I wasn’t dieting at all. According to the theory, my fat cells are releasing fat easily because my insulin levels are low, which means I don’t have internal starvation, which in turn explains my complete lack of hunger.

Also in the book: he claims we don’t actually know eating saturated fat raises cholesterol, nor that high cholesterol causes heart disease except when it’s super high, but then again it also seems to be bad to have super low cholesterol.  I gotta hand it to this guy, he’s not afraid of going against conventional wisdom, at the risk of being ridiculed, which he most definitely has been.

But that doesn’t make me dismiss his theories, because I’m pretty sure he’s right when he says epidemiology is fraught with politics and bad selection bias.

It’s certainly an interesting book, and who knows, he may be right on some or all scores. On the other hand, maybe it doesn’t matter that much – not many people want to or are willing to avoid carbs, and maybe it’s not environmentally sustainable, although I don’t eat more meat than I used to, just more salad.

We are now ruling out the idea that people don’t exercise enough as the cause for being fat, and as we’ve attempted to follow the advice of the so-called experts, everyone seems to just get fatter all the time. As far as I’m concerned, all conventional bets are off.