Calorie restriction is typically done by cutting fat, which means adding more carbohydrates. Carbs raise blood sugar, which triggers insulin. Insulin tells your body to store excess blood sugar AS FAT. Cutting calories more can result in lowered metabolism since the high insulin level prevents your body from accessing stored fat for fuel. Keto (low carb high fat) diet is specifically designed to minimize the rise in blood sugar and therefore minimize the rise in insulin level. Once your body gets adapted to burning dietary fat for fuel instead of carbohydrates (this takes a few days to a few weeks) and with low insulin levels, then your body can easily BURN STORED FAT for fuel, too. YAY! Weight loss. For me, the biggest problem with calorie restriction is that I am always feeling so hungry