If you’re keeping your carbohydrate intake under 20 grams a day and your protein intake around a gram a day per kilo of lean body mass, then if you’re getting that hungry that quickly, you’re not eating enough fat. The whole point of a low-carb, high-fat ketogenic diet is that you eat fat until you’re satisfied, regardless of how many calories you end up consuming. You’re body will tell you when it has enough fuel, you don’t need to calculate it.
I remember the day I finally had enough fat. I was halfway through the meal, and it became clear I didn’t want to eat any more. In fact, the thought of eating any more food became slightly unpleasant, because I’d finally had enough to satisfy me. On my previous way of eating, I was constantly hungry. I could have a belly-full of spaghetti and still want more.
Now I find myself satisfied at the end of a meal, and I can go hours without thinking of food. I eased into keto, going fully keto sometime in June. Back in March I was at my heaviest ever, 247 lbs. Now I’m down to around 200 lbs. And all by eating as much as I wanted.