The Truth About Burning Fat

There is a difference between starvation, prolonged fasting and controlled carbohydrate eating. 

Even there are almost similar mechanisms in terms of metabolism working, it is important to understand the difference to a carbohydrate diet.

The whole process of muscle protein catabolism and liver gluconeogenesis is regulated by glucocortiosteroids and glucagon and a relative lack of insulin.

Early in fasting glycogen reserves are depleted, and protein (mainly from muscle) becomes the major source of carbon for glucose production.

Glucose is required in substantial amounts by blood cells and the central nervous system on a daily basis. 

There is no initiation of ketone body production by the liver to provide a more water soluble form of fat-derived fuel.

A very similar adaption of protein and energy metabolism occurs in person consuming diets very low in carbohydrates, where there is little or no glycogen reserve.

However, in this instance, dietary protein largely or fully substitutes for muscle protein in gluconeogenesis. Even when discussing starvation most critics of low carb diets miss the boat. 

The body adapts to starvation and reduces the need for protein-dependent gluconeogenesis by boosting its production of ketones, a fuel alternative to glucose for most cells.

Circulating ketones reach maximum level after about ten days of fasting and now substitute for much of the glucose requirement of the central nervous system. 

With that the need for catabolism of protein in the muscles is extremely reduced. The excretion of urinary nitrogen declines when the protein catabolism is reduced.

And there is a shift from the excretion of urea to a predomination of ammonia loss. This shift toward ammonia versus urea parallels the increased production and excretion of keto acids and serves to maintain the acid/base balance.

It is important to know that muscles are a carbon reserve and might be used for the production of glucose if needed.

Keto diets help the body to burn fat instead of carbohydrate just to use it as an energy source. Keto diets also help in maintaining a healthy shape of the body for a long term.