A link in comments reminded me of a criticism of Good Calories, Bad Calories I see now and then. In a nutshell, the criticism goes like this:
Taubes says people get fat because insulin makes their fat cells release fatty acids too slowly, so they have to eat more to avoid cellular starvation, and then they get fat. But studies show fat people have the same concentration of fatty acids in their bloodstreams as lean people. So there. That proves Taubes is wrong.
Uh, no. The fact that fat people have a steady supply of fatty acids in their blood doesn’t prove him wrong at all. The people who think it does either didn’t actually read Good Calories, Bad Calories or didn’t grasp one of the key concepts.
Let’s start with an analogy. Suppose we’re studying people on a planet where it’s considered disgusting to have a large savings account. And yet many people do. I want to understand why, so I spend years digging through financial research. Then I offer this explanation:
For half of each year, people on this planet have no regular income and have to live off the interest from their savings accounts. Most accounts pay 10% interest, so most people continuing saving until the 10% interest provides enough cash to pay their bills.
However, because of a banking flaw, some people’s accounts pay less than 10%. At the lower rate, the interest they can withdraw isn’t enough to pay their bills – that is, unless they compensate by making bigger deposits to build up more savings. So they do. Each time the interest rate drops a bit, they deposit and save more until the interest is once again enough to pay their bills. For people whose accounts pay a low interest rate, this requires a BIG savings account.
With me so far? Great. Now suppose another researcher digs up a study showing that people with fat savings accounts withdraw the same amount of cash each month as people with normal savings accounts. Waving that study around, the researcher makes this announcement:
Aha! Naughton is clearly wrong! He claims people grow fat saving accounts because they can’t withdraw enough cash as interest. But now we know people with fat accounts are withdrawing just as much cash as everyone else. So he’s wrong. Wrong, wrong, wrong!
You see the flaw in that conclusion, right? The fact that the fat-account people are withdrawing enough cash to pay their bills doesn’t prove my explanation is wrong – because I never claimed they don’t end up withdrawing as much cash as everyone else. I said they maintain big accounts so that they can withdraw as much cash as everyone else. The researcher didn’t read or didn’t understand my explanation of how these people solved the defect with their low-interest accounts. He apparently stopped reading after the description of the defect itself.
Let’s return to our own planet. Here’s my quick, user-friendly summary of some lengthy passages in Good Calories, Bad Calories.
To keep your blood sugar in the normal range, your body needs to alternately store and release fatty acids. When glucose goes up, your body brings it down by storing fatty acids and burning glucose as the primary fuel. But as glucose continues to drop, your body prevents it from dropping too low by releasing fatty acids for fuel. As most of your body switches to burning fat, glucose is preserved for the brain – which requires at least some glucose every minute of every day.
If you can’t release a sufficient supply of fatty acids, you have a problem. When glucose drops after meals (not to mention during the long night’s sleep), your body will experience a fuel shortage. You’ll be hungry. Your brain may sense a threat to the consistent fuel supply it needs. If this is a regular experience, it’s a problem your body must and will work to fix.
That’s the quick summary. Now here are some paragraphs from what I consider the most important section of the book, offering an explanation of how our bodies fix the problem (bold emphasis mine):
If energy goes into the fat tissue faster than it comes out, the energy stored in the fat tissue has to increase. Any metabolic phenomenon that slows down the release of fat from the fat tissue – that retards the “energy out” variable of the equation – will have this effect, as long as the rate at which fat enters the adipose tissue (the energy in) remains unchanged, or at least does not decrease by an equal or greater amount.
Pennington suggested that as the adipose tissue accumulates fat, its expansion will increase the rate at which fat calories are released back into the bloodstream (just as inflating a balloon will increase air pressure inside the balloon and the rate at which air is expelled out of the balloon if the air is allowed to escape), and this could compensate for the initial defect itself. We will continue to accumulate fat – and so continue to be in positive energy balance – until we reach a new equilibrium and the flow of fat calories out of the adipose tissue once again matches the flow of calories in.
By Pennington’s logic, obesity is simply the body’s way of compensating for a defect in the storage and metabolism of fat. The compensation, he said, occurs homeostatically, without any conscious intervention. It works by a negative feedback loop. By expanding with fat, the adipose tissue “provides for a more effective release of fat for the energy needs of the body.” Meanwhile, conditions at the cellular level remain constant; the cells and tissues continue to function normally, and they do so even if we have to become obese to make this happen.
So to sum up:
According to Taubes, if our fat cells begin releasing fatty acids more slowly, we get fatter to overcome this defect. Once we’re fat enough to release a sufficient supply of fatty acids, our weight tends to stabilize again. We’re back in a state of energy balance. We now store and release fatty acids as needed, just like thin people – but we had to get fatter in order to do so. If the fat cells slow their rate of release again, we become fatter again to compensate. That’s how our bodies stay in a state of energy balance.
Nothing in that explanation says obese people release fewer fatty acids into their bloodstreams than thin people. It says they achieve a normal supply of fatty acids by being fatter. That’s why (according to the book) our bodies fight to gain and keep the fat – because if we can’t release enough fatty acids between meals, we can’t keep our cells fed and our glucose levels stable. To shed body fat without fighting our own bodies, we first have to fix the root of the problem. (That’s where the change in diet comes in.) Once we can release enough fatty acids with a smaller fat mass — because the rate of release speeds up again — our bodies will be willing to lose the extra fat.
Again, I consider that one of the crucial ideas – perhaps the most important idea – in the entire book. I don’t know how anyone could miss it. But apparently plenty of people did.
During between-session chit-chat at a conference some years ago, a blogger whose name I won’t mention tossed out the line about how fat people have just as many fatty acids in their bloodstreams as thin people, so Taubes is wrong and therefore the insulin hypothesis is wrong.
“Well, actually Taubes wrote that each time our fat cells become a little slower at releasing fatty acids, we get a little fatter to compensate,” I replied. “Fat people release as many fatty acids into their bloodstreams as thinner people, but they need more fat mass to do so. That’s why they’re fat. Being fat keeps them in a state of energy balance.”
That drew a look of confusion from the blogger, who then replied, “Hmm, I don’t remember that part of the book.”
I didn’t say anything, but I was thinking, YOU DON’T REMEMBER THAT PART OF THE BOOK?! Are you @#$%ing kidding me? That’s like reading Huckleberry Finn and not remembering the part about the runaway slave.
Don’t get me wrong here. I don’t have a problem with people disagreeing with Taubes, challenging the insulin hypothesis, offering their evidence to counter his, whatever. That’s how it should be. Real science is not (despite what some politicians believe) about reaching a consensus. We should always be questioning and re-assessing our beliefs.
But when people argue that Good Calories, Bad Calories got it all wrong, it would be nice if they read the book first. And then remembered what they read.