For decades now, I have believed that polyunsaturated fat from sources such as corn oil, soybean oil, safflower oil, and canola oil is a very bad idea. They are highly prone to oxidation and associated with all kinds of diseases. But the more I researched, I was coming to the inevitable conclusion that monounsaturated fat could also contribute to obesity. That was the beginning of the croissant diet.
Monounsaturated fat has always been a kind of happy middle ground for traditional nutritionists who have moved away from promoting soybean oil and Weston A. Price people who promote butter. No one ever really has anything bad to say about olive oil. But everything I learned suggested that olive oil could cause weight gain.
How the Diet Works
Here is my nutshell version of how this works (once again, a shout out to Hyperlipid for figuring this out, I didn’t): The primary mechanism by which the body stops the flow of energy into fat cells is the production of free radicals, aka Reactive Oxygen Species (ROS), at the conserved molecular bottleneck in the electron transport chain of the mitochondrial inner membrane. The ROS block the activity of several proteins involved in insulin signaling, leading the fat cells to become physiologically and reversibly insulin resistant. The job of Insulin is to send a signal to tell fat cells to store energy. If the fat cells are (temporarily) insulin resistant, they won’t take in any more energy. Fat loss will occur. Long-chain saturated fats create lots of ROS. Unsaturated fats don’t.