Hour 12
Fat Burning Begins
The metabolic switch is beginning. This is the threshold that most overnight fasting protocols aim for.
What's Happening
Liver glycogen is significantly depleted. The liver is now actively producing ketone bodies from fatty acids. Fat oxidation has meaningfully increased. Growth hormone begins to rise, protecting muscle tissue.
How You're Feeling
The hunger wave often peaks somewhere here and then softens. Many people experience a surprising calmness after this point — the body has committed to fat burning and stops expecting carbs.