Gary Taubes is so obsessed that “carbs make us fat”, that he thinks we could (should) eat unlimited fat, as long as we don’t eat any carbs. Who the ^#%$ wants to do that? Sure, I like bacon and eggs, but I’d rather eat sensibly than follow some tortuous ketogenic diet that doesn’t work (see below).

I prefer to eat low-fat (< 10% of calories), knowing that I can eat unlimited carbs, exercise moderately, and not risk gaining fat. This is because the body can't readily turn carbs into fat (de novo lipogensis is slow). However, any excess dietary fat will be quickly stored as body fat.

Gary Taubes takes the same understanding of the body’s mechanisms (that we preferentially burn dietary carbs and store excess dietary fat), but reaches a different conclusion. He reasons that if you don’t eat any carbs, then you can’t store any fat. WTF?! How do you make that conclusion? This logical error is called the fallacy of the inverse (If A, then B. Therefore, if not A, then not B. Not!) Here, A = “overeating carbs AND fat”, and B = “we become obese”. So “overeating fat BUT eating no carbs” is not A, therefore not B, and we don’t become obese. Not!

Some people realise this can’t really be true, and aren’t surprised when they hear about people (like Jimmy Moore) gaining weight on a ketogenic diet (< 30g/day carbs). That's exactly what a caller to Sean Croxton's Underground Wellness podcast asked (could you over-eat fat, without any carbs, and not gain weight?). Here’s Gary Taubes’ response (starts at 4:00):

… but I do not believe you can get fatter [no matter how much fat you eat, when you eat no carbs], and for most people, probably some huge proportion, 80% – 90%, if you’re not eating carbs, your’re going to lose weight, you’re not going to gain it.

So to me, its the carbohydrates that literally make you fat. You will store the fat that you eat. See, what happens when you eat the carbs and your insulin levels go up, you store the fat, the dietary fat, while you burn the carbs. And if your insulin levels stay up, you never let that dietary fat that you stored out of your fat tissue. So the carbs are still the problem, even though the fat is being stored first.

So he understands the well-known “fat-sparing” effect of eating carbs. Carbs are preferentially burned while the fat is stored. So most reasonable people eat low fat to minimize its storage. (Our bodies were made to store fat. It’s a great survival feature.) But Gary Taubes thinks we can trick the body into not storing excess dietary fat, by not eating any carbs. Good luck with that.

Then he goes on:

And because of that, we’ve been told, “Well, since we’re storing the fat and burning the carbs, if you don’t eat the fat, or if we eat less of it, we’ll store less of it.” But the carbs are controlling how the fat tissue is holding on to the fat, and whether it’s releasing it to be burned later.

So the carbs are basically what’s regulating the insulin and the insulin is regulating the fat and the dietary fat is only a problem if you’re eating a high carb diet.

He’s saying that low-fat diets don’t work, because carbs never let the fat out of the adipose tissue. But, there are plenty of times where the body burns fat, like in between meals, during moderate exercise, while you’re sleeping, etc. Sure, if you constantly keep eating, you won’t access your fat stores, but in most normal people, adipose tissue is metabolically active. Excess fat goes in when eaten, and comes out as needed. (Hey, what would happen if you didn’t eat any excess dietary fat?)

Argh. You know, if you like bacon and eggs, then eat them. If you want to eat ketogenic, then good for you. And if you want to believe that carbs make you fat, no matter what the science says, then hopefully the low-carb approach works for you. But if you go around arguing that there’s a metabolic advantage to eating no carbs, please try listening to reason occasionally.