Originally Posted by David Mathews
When I started eating paleo/low carb I was under the impression that you would need to get into ketosis to burn fat for the production of glucose in the liver thus slowly depleting fat stores. However, from reading some of Robb's writings,Dr.Eades,Gary Taubes and some others it appears that just eating low carb/high fat and keeping the insulin in check will afford the fat burning advantage without necessarily going into ketosis. Am I on the right track?
David, you can lose fat and preserve muscle without even restricting carbohydrate if you are in energy deficit (ie a calorie deficit), let alone being in ketosis. The success of organizations like Weightwatchers are testament to that. Nevertheless it is neither a very easy (constant hunger) method for all but a lucky few, and a very unhealthy one if you are human (this species is simply not metabolically designed to get more than a small proportion of energy needs from carbohydrate).
Also, producing and using very many ketones is only a fill in mechanism for supplying bodily energy needs when carbohydrate is restricted. Traditionally living Inuit are only ever in mild ketosis (remember, even high carbers are in some degree of ketosis when they wake up after their normal sleeping fast) their entire lives and yet they eat practically no carbohydrate. The longer you spend low carbing the better you become at using free fatty acids without the liver having to make ketones to supply energy needs. Some ketones will always be produced for tissues that cannot use FFA's directly (eg. CNS), and AFAIK heart muscle actually prefers ketones to FFA's.
The other thing is that peeing on Ketostix is a completely unreliable way of determining whether you are producing a lot of ketones. After all, if they are all being used, none will show up in your urine.
How long does it take for the body to become fully fat adapted (i.e. to be able to use FFA's almost exclusively in preference to ketones)? I've no idea, but at least a year of restricting carbohydrate 24/7. PWO carbs will guarantee that you never become fully fat adapted and be doomed to fruity breath forever. You can replenish glycogen from intramuscular triaglycerol without any carbs whatsoever anyway, it just takes a bit longer. The research to determine whether that process can ever be as efficient as doing it with glucose has not yet been done. There aren't that many really long term low carbers around. And even fewer traditionally living Inuit, more's the pity. My personal guess is that it won't, but the other metabolic damage carbs do make the decision of which glycogen replenishing mechanism to try to encourage a no brainer IMHO.