During even a brief period of fasting, your metabolism can rapidly change.

For example, let’s look at the macronutrient carbohydrate, like those found in rice, breads, and fruit. The storage form in our bodies, glycogen, generally decreases, which can shift metabolism from burning carbohydrates to burning fat for energy.

This occurs in multiple tissues including the one responsible for movement, muscle.

This challenge involves Intermittent Fasting to speed up metabolism and aid in fat burning. A recent study confirms fat burning is vastly increased during fasting, but even more interesting is its effects on muscle.

Muscle can use both carbohydrates and fat for energy and can adapt to different nutrient intakes including fasting (2). This occurs through a complex, energy and nutrient-sensing pathway that is involved with many different energy states, like being full or fasting (3). Understanding this pathway under different dietary conditions is very important as it can affect how genes are expressed and regulated (1).

Not surprisingly, during short duration periods of fasting there is a rapid decrease in carbohydrate oxidation (sugar burning) with a large increase in fat oxidation (fat burning) mostly in muscle.

Insulin and leptin (a hormone involved in appetite control) levels also decrease as free fatty acids and growth hormone levels increase. 

Additionaly, 23 genes involved in the regulation of metabolic processes, have been found to be significantly affected by fasting at both early (10 hours) and late (24 hours) time points. Many of these genes helped move metabolism to fat oxidation (fat burning) at the whole-body level.

In relation to fat burning in muscle tissue, short-term fasting is quite effective. However, prolonging the daily fast or fasting too often to speed up fat loss is not advisable as fasting for too long can cause a loss in muscle mass and negatively affect metabolism (2;3).