Explain the adage "fats burn in the flames of carbohydrate"

This expression has been resurrected lately with the resurgence in popularity of ketogenic diets (aka, low-carbohydrate, low-carb diets) and their role in ketosis.

Explanation:

Simply, carbohydrates need to be present in order for fat to be utilized as energy. If a low level of carbohydrates exists, a substance known as pyruvate begins to build up. Pyruvate is formed during glucose metabolism and if glucose is not present, pyruvate cannot do its job in the energy process.1 Therefore, fat has nowhere to attach in the body’s mitochondria, which in turn slows the metabolism, and will halt or extremely lessen the body’s fat-burning capabilities1. Furthermore, when the body lacks carbohydrates, critical amino acids are stripped out of muscle tissues as the body turns against itself (effecting amino acids such as branched-chain amino acids and alanine, as carbohydrates spare proteins). The moment the amount muscle tissue is decreased, the body’s metabolic rate is lowered substantially.

ia. mver.y..sor .r..yinee..i am.ina.rush.pleas eforg.ive   meiknowiama. nas.s holei apalo.gize

d, i believe because of it's activity level