I’ve read the main part of the theory behind Dr. Rosedale’s diet in his book and some of the practical application. What follows is my summary of that information.
Dr. Rosedale says that the body can burn fat or sugar, but it won’t burn both at the same time. He claims that a diet high in carbohydrates causes the body to get stuck in sugar burning mode. When there is too much sugar in the blood, the excess gets stored as saturated fat. That would be fine if we could then switch to fat burning mode and burn the fat when the sugar is used up. But that, Dr. Rosedale claims, is not what happens. As we get older, our ability to switch between sugar burning mode and fat burning mode diminishes. So when someone in sugar burning mode runs out of sugar to burn, his body cannibalizes the protein from its muscle and bone to make sugar to burn. The fat remains in the fat cells. This is why someone who loses weight on a typical low-fat/high-carb diet loses muscle and ends up being a smaller version of a fat person.
A low-carb/high-protein diet does not correct this problem since excess protein in the diet is converted into sugar, and that raises blood sugar, too, and the body ends up remaining in sugar burning mode. The body does not store protein, so the body still ends up cannibalizing muscle and bone when the supply of sugar and dietary protein runs out. When protein is converted to sugar, the nitrogen atoms are stripped from the protein in the form of urea and ammonia, and this becomes a toxic waste product that the body must deal with. So really, a diet that includes excess protein is toxic. Dr. Rosedale recommends getting 50 – 75 grams of protein from the diet, which is consistent with RDA recommendations.
So that leaves fat as a preferred source of fuel. But not all fats are healthy. Dr. Rosedale recommends getting fat from fish and fish oil, nuts and nut oils, avocados and avocado oil, olives and olive oil, and coconut oil. He recommends eating lean poultry, limited amounts of lean meat, and low-fat dairy from properly raised animals to avoid the saturated fat content. Properly raised animals means grass-fed or pasture-raised and animals raised without added hormones and antibiotics, not the CAFO animals typically sold in supermarkets. The diet also includes generous amounts of non-starchy vegetables and some berries.
As an aside, Dr. Rosedale did mention the link between depression and low-fat diets, which has been my primary contention against them and why I have increased the fat in my NutriSystem plan, having myself suffered from depression that I now believe was a result of low-fat dieting.
Dr. Rosedale also claims that his diet is de-aging. The low-carb content of his diet gives the life-extension benefits of a calorie-restricted diet without having to go hungry. In other words, he is claiming that his diet can reverse age-related degeneration. This is due to the low insulin and leptin levels maintained while on such a diet and the proper functioning of these hormones. Dr. Rosedale’s diet is a lifestyle diet. His list of benefits from his diet is quite long, and there isn’t space to list them all here.
The general theory behind Dr. Rosedale’s diet makes sense to me and agrees with my experience of dieting. I have lost weight on a high-fat diet before. I also believe that I have suffered harm from low-fat diets as Dr. Rosedale says we will, namely my worst depressions have coincided with stints of low-fat dieting. Dr. Rosedale’s theories also explain a lot about why we yo-yo and how fat can end up in the arteries, among other effects that can result from the derangement of insulin and leptin functioning. I’m not sure about Dr. Rosedale’s recommendation to minimize animal fat. I do agree that ideally the animals should be pasture-raised if one can afford to buy such since grain feeding alters the balance of the polyunsaturated oils from healthy omega-3 to harmful omega-6. But I also have been led to believe that animal fat contains important fat-soluble nutrients that are difficult to get from other sources. Therefore, meats and dairy should include their fats. My previous foray into veganism and subsequent detriment would support this conclusion.