Another one of the fallacies that seems to pervade is that a ketogenic diet is the same as being in starvation – whereby the body significantly reduces it’s metabolism and starts tapping into the muscles for energy. This is completely bogus and you’d be best off just ignoring the idea altogether.
In light of restricted carbohydrates through either keto or starvation the body will focus on maintaining glucose homeostasis, ie constant blood-glucose level. It’s highest priority is to provide sufficient energy to the brain and other critical functions, and can do so with a mix of glucose and ketone bodies.
The only real common ground is that ketone production is elevated in both a keto diet and in starvation due to reduced carbohydrate intake. Conflating keto with starvation is guilt by association – eg falling asleep makes you unconscious; being punched out also renders you unconscious and can cause serious injury; therefore falling asleep is dangerous like being punched out.
Starvation is just that – severe restriction of calories over a long period, and “starvation mode” is what anti-low-carb people tend to call it as a scare tactic. After a few days of complete fasting the metabolic rate only drops 5-10% – sometimes increases – and even on an intake of half the amount of energy you’d normally consume for maintenance, you would be fine for months without too much of a drop.
If you have a significant amount of fat to lose then your metabolism will barely drop at all, even on severe restriction your extra adipose stores will make up any energy requirements you have. A ketogenic diet stabilises glucose and maintains very low levels of circulating insulin, so access to liberating energy from your adipose stores is unhampered.
A ketogenic diet is extremely protein sparing, the idea that you need carbohydrates to stop your muscles from wasting away is a complete fairytale. As long as you have enough energy available via consumption and adipose stores there’s no need to stress, it’s ridiculous to even consider that your body is stupid enough to rip apart your structural tissues for the meagre glucose spine for energy – a very metabolically expensive process with a tiny yield.
Significant lean body mass destruction only begins to occur when you don’t have enough glucose OR ketones available, both of which are generated by burning your fat stores, meaning the starvation mode of using up muscle tissue for glucose/energy only happens when you have very little stored body fat available and aren’t getting it in your diet – ie extremely lean and actually starving.
Lipolysis (release and busting apart of fat from adipose stores) is a precursor to gluconeogenesis (creation of glucose), what happens is that when the triglycerides are released from your adipose it also releases glycerol, this glycerol can then head to the liver and be converted to glucose for use in the blood, the brain, and to replenish glycogen. Dietary protein can also undergo gluconeogenesis to the same end result.
The way it’s explained in Wikipedia: http://en.wikipedia.org/wiki/Fatty_acid_metabolism#Transport_and_oxidation
“When insulin levels drop in response to low blood glucose levels, this triggers an intracellular secondary messenger cascade that phosphorylates hormone-sensitive lipase to break triglycerides into glycerol and free fatty acids for use in metabolism, a process called lipolysis.”
“When the body uses stored fat as a source of energy, glycerol and fatty acids are released into the bloodstream. In some organisms, the glycerol component can be converted into glucose by the liver.”
This is one reason why keto is known as very muscle sparing, if you are losing a significant amount of weight, you can expect some of that will be lean body mass – but in the way you think of “use it or lose it”, ie, your body is no longer needing to support as much weight and so it will reduce somewhat, you’re not just wasting away.
In the end the point is that the only real thing starvation has in common with a ketogenic diet is elevated ketone production, which substitutes for glucose as fuel for the brain and other stuff – the mechanism of how this occurs is through carbohydrate restriction – which is the one commonality of keto and starvation.
Just keep on eating plenty of fat and enough protein – you certainly won’t starve.
Further reading on actual starvation: http://www.ncbi.nlm.nih.gov/books/NBK22414/
“Food Intake and Starvation Induce Metabolic Changes” – Biochemistry. 5th edition.