Mr Ludwig has been proven wrong on this theory time and time again.
Insulin spikes or just insulin doesn't cause weight gain.  You get the same rise in insulin from beef as bread. One carb the same response as one protein. Therefore by this theory both will make you fat. Not true. It's easily consumed calories in excess that's the problem. ITS NOT INSULIN.

Look, I’m no expert, I’m an optimistic believer, I like the ideas of low carb, keto, paleo etc. But then explain to me, why bodybuilders and endurance athletes almost entirely eat high carb diets. Explain to me, why other sources tell me that insulin is anabolic and stores glycose in muscle tissue. I think we must find a
common ground between CICO and Insulin. I don’t buy in anymore on either side. It’s both. And many more. However thanks CrossFit for sharing controversial ideas and different opinions. 

Wow, would not expect something so stupid from a big company like crossfit. If you watch crossfit athletes the majority state that they consume around 500 g of carbs/day, does CIM doesn't work if you are an athlete. Also for every study that sustain CIM there tens that doesn't. 

For many of us, Gary Taubes's Good Calories Bad Calories provided the first exposure to this apparently-counterintuitive idea. But as we thought about it, so it increasingly seemed plausible: after all, the targeted deposition of fat in adolescent women is hormonally-driven; and it's striking that the federal government first advises us to eat more carbohydrate and less fat in 1977, we do, and obesity rates accelerate from 1980.
i know that this idea has been tested experimentally by Taubes and others, but I'm not sure If a consensus has yet emerged of what those studies have shown.