In intermittent fasting, what essentially takes place in the body is that one source of energy — which can facilitate the accumulation of body fat — is switched for another.
Our bodies run on glucose or simple sugar, but when we fast for a longer period of time, that energy source becomes unavailable.
Our system needs to identify a different kind of “fuel.” That is when the body begins to convert certain types of body fat into fatty acids, which are easily absorbed by the blood.
Fatty acids, in turn, produce molecules called ketones, which the body uses as its new source of energy.
Stephen Anton, a researcher at the University of Florida College of Medicine in Gainesville, calls this process “flipping the metabolic switch.”
“This switch,” explains Anton, “can happen after a certain period of time fasting. It’s a gradation in which your metabolism over time shifts to using higher and higher amounts of ketones for energy.”