Here's my impression of what happened:
The keto train pulled into the station. Mercola perceived that it was going places, so he hopped on while he could. He was all excited about all the places he might be going; He got caught up in all the excitement on the train and started shouting out the windows as the train picked up speed. He didn't fully comprehend the entire story, but he listened to others on the train & pieced together a narrative. Except, he wasn't content to just be another passenger. So, he came up with an angle he thought he could use to differentiate himself. MMT, that's it! MMT wasn't the same as ketogenics because MMT focused on the effects on the mitochondria, not on how those benefits came about. Mercola tried to claim that his method (which he never actually defined nor successfully differentiated from ketogenics) also had some of the other benefits of ketogenics (beyond mitochondrial health), but didn't go into much detail, because HIS focus was on the mitochondria.
My thoughts about the book:
If you're still trying to figure out what to believe about a ketogenic diet, don't be swayed by Mercola's hype. He doesn't present evidence for any of his wondrous claims. He also claims that his Mitochondrial Metabolic Therapy (MMT) approach is somehow different than a ketogenic approach because one has the goal of being in nutritional ketosis, while the other has the goal of keeping your body in a fat-burning mode. They're exactly the same thing. He says that "ketogenic diet" "implies that the whole purpose of the diet is to have as many ketones around as possible." Hogwash.
Mercola criticizes other publications/advocates for basing their positions on studies that are not scientifically sound, studies that are not randomized control trials. Yet, he then supports his suppositions in exactly the same way.
For example, he cited Jimmy Moore, author of Keto Clarity. What expertise does Jimmy Moore have? None. Moore's book was about HIS experience with a ketogenic diet, with a whole bunch of quotes from various types of "experts" expressing their opinions.
In other places, Mercola doesn't even cite any references. He claimed, for example, that "the lower your average insulin level and the better your insulin receptor sensitivity, the slower the aging process." On what does he base this claim? Oh wait, he continues, "In fact, according to studies of the planet's oldest people, lower insulin levels and higher insulin receptor sensitivity are associated with longer life." Mercola should know better than this. "According to studies": What studies? What kind of studies were they? Who did the studies? "The planet's oldest people": How many people? How old were they? Where did they live? What kind of lifestyle did they have? "Associated with longer life": Associated with? That proves nothing. Is there a causal relationship? Are there other factors that had more of an influence on longevity than insulin level? This is exactly the type of non-scientific, pie-in-the-sky non-study Mercola was complaining about others using.
After espousing the benefits of his nutritional program throughout most of the book, once he gets to the end, he cautions that he, himself, now wears a constant glucose monitoring system because his diet caused his blood glucose reading to go up. WTH?
It seems like most of the authors I've read who are writing about ketogenic diets simply regurgitate what others have said, cite them as references, and neglect to look at actual scientific support for their theories. There are two people I follow on YouTube who do actually look for scientific information: Dr. Darren Schmidt and Dr. Ford Brewer. Their presentations on YouTube aren't going to win over the masses, but they do critically analyze the studies.
For the record, I do subscribe to the ketogenic philosophy of nutrition. I picked up this book because I'm looking for a good, straightforward, non-intimidating way to introduce others to this way of eating. This book is not it.
I think that Mercola has discovered the wonders of being a published author and has now made book writing his primary goal. He seems to be an expert on so many different aspects of health and is writing separate books on each angle. Just take a look at the list of books he has published. By reading five of them, Mercola will tell you how to combat cancer, boost brain power, increase energy, sidestep illness, shed excess weight, help your body fix itself, prevent disease, prevent premature aging, optimize weight, live longer, conquer carbohydrate addiction, stay slim for the rest of your life, take control of your health. Are you noticing the overlap? I'm going to take a wild guess and suggest that all of these books will say pretty much the same thing as Fat For Fuel. And, none of them will map out a step-by-step plan for following his advice. Truthfully, some of his recommendations seem contradictory to some others.
Fat For Fuel gave advice about which foods to eat/avoid for mitochondria health and gave suggestions for ways to fast. Mercola told us which way he prefers, but admitted that no studies have been done on the long-term effects of this type of fasting. Mercola also tells us about many other types of therapy, beyond burning fat for fuel, for mitochondria health. The last two chapters are devoted to suggestions unrelated to burning fat for fuel. I'm guessing this advice will be in all of his books, regardless of the book title. Each book is likely just another ad campaign for the same product.
Don't be swayed one way or the other by Mercola's assertion that this is a science heavy book. It isn't. It doesn't even talk about processes mitochondria use. It talks about some things that can affect mitochondria, but never explains how the mitochondria work or how fat or glucose is used.
Because of its shortcomings & exaggerations, I found this book quite annoying to read.