Many people who knew me during the 1990s are surprised that today I no longer recommend low fat diets. Indeed, during the whole of that decade and well into the first few years of the new millennium I was a staunch advocate for dietary fat reduction both as a means for achieving long-term weight loss and for general human health.
Before I talk about what changed my mind, I want to mention what did not. Namely, the Atkins diet did not change my views on low-fat diets. The problem, for me, with the Atkins diet at the time (late 1990s) was that it was a fad and not a scientific breakthrough. Sure, people who followed that diet lost weight, but then people who follow almost any diet lose weight and I believed then as I do now that very low carbohydrate diets are more a gimmick than a sustainable lifestyle. On the other hand, I must admit that low-carb diets, Atkins in particular, paved the way towards a fresh examination of nutrition science that opened-up a field that had grown pretty dogmatic and ossified. And from that opening emerged the principles that I now teach.
The science that changed my mind about diet included the following:
It's not that I believe that low fat diets are harmful but that in light of the issues cited above, they miss the mark in two ways: first that they tend to be (but don't have to be) high-glycemic and high sugar and second, that they tend to be far too low in omega-3 and other essential fats. More concretely, they just aren't as healthy or effective or easy as the sort-of modified paleolithic-cum-Mediterranean diet that I now teach.