Amino acids come from ... PROTEIN ... period.

Carbs are broken down in the intestinal tract into SUGAR ... period.

The amine portion of amino acids must come from nitrogen, and protein is the only macronutrient that contains nitrogen. Fat and carbohydrate are made of molecules of carbon, hydrogen and water. No nitrogen. No amine. Nada.

Carbs are not involoved in protein synthesis or amino acid production in any way. That being said, your liver can make glucose (carbohydrate) out of protein if necessary. There are a few tissues that require a tiny amount of carbohydrate every day. Most of the respected low-carb programs are just that - LOW carb, not NO carb .. so you will be getting enough for healthy function.

When you burn fat, it breaks down into fatty acids, which get sent to the liver to be converted into ketones. Your muscles use ketones very efficiently for fuel, when glucose levels are kept low.

I'm not an expert, but my understanding is that for optimum muscle building and strength, you need to be fuelling your muscle with either ketones OR glucose (glycogen) but not both at the same time. There is a program used by body builders called the Cyclic Ketogenic Diet, or CKD. Also known as the Body Opus. It's a carefully controlled low-carb regimen for 5 days, followed by a carb-up for 2 days ... and a very specific, intense work-out routine to get maximum benefit from both the ketone and carb fuel. Check out our Exercise Forum. You'll find a subforum all about CKD and Body Opus, with tons of info from our moderator, Trainerdan -- a personal trainer and body builder himself. He's outlined the CKD quite thoroughly in the thread CKD 101; check it out here.

hope this helps,

Doreen