You DO NOT have to add extra fat to eat a lchf diet, just by reducing the carbs in your diet will automatically increase the percentage of fat.
I managed to lose 5 stone and control my diabetes by eating a low carb normal fat diet, I never added extra fat as fat has too many calories and I wanted to lose weight.
Im sure I couldnt have lost the weight I did had I added extra fat/calories to my diet, in fact when ever I ate extra fat, say cheese after diner or extra cream or fried breakfasts I would see my weight loss stall until I stopped eating the extra fat, weight loss is a fine balance between eating enough but not too much.