The primary reasons people fast are to accelerate weight loss and trigger autophagy—a metabolic process that removes dead and harmful cells.
On most diets, you can only enter a fat-burning state and activate autophagy by deliberately starving yourself, as insulin disrupts both processes. Since fasting is essentially controlled starvation, it becomes necessary for those whose diets keep insulin levels elevated.
However, on a carnivore diet (which is inherently ketogenic), insulin remains low because your body primarily relies on ketones for energy rather than frequent blood sugar spikes. This allows autophagy and fat burning to occur naturally as needed, making intentional fasting unnecessary when following an optimal diet.
Fasting for a notable period on a carnivore diet may give you the inverse of the desired effect, as when you tell your body there is a lack of food, it metabolically enters a fat storage state.