Ketosis is a great appetite suppressant; if you are eating a standard (high-carb) American diet, you have blood sugar swings that can cause bouts of intense hunger—sometimes within as little as two hours of eating a meal!
When you enter ketosis and start burning fat for fuel, your blood sugar will stabilize at a lower, healthier level. The healthy fat will be metabolized into ketones by your liver, and that will suppress your hunger via several metabolic pathways.
When it comes to most hunger pangs, we’re talking about ghrelin, not leptin. Ghrelin is the main hunger hormone and increases appetite. When you eat, ghrelin levels drop, if you are overweight they won’t drop as much as they should. When you start to lose weight on a non-ketotic diet, your body senses that it’s being starved and ghrelin levels increase. This is one reason regular diets often fail. The good news if you’re on a ketotic diet is ghrelin levels do not increase as you lose weight.