I had similar difficulty when I first tried LCHF. gained almost a stone in 3 weeks. Probably took too literally the 'eat until you have had enough, or until full'. I am not sure that advice works for everyone.
Instead, when I am not using Newcastle diet methods, I limit the amount of high calorie fats such as cheese, butter, cream, and just make sure I keep carbs to a minimum, eat fresh food, no bread, potatoes, pasta rice or beer, never eat sugary foods either, making sure that dairy ( yogurts etc) is full fat. This is my own version of a low carb diet with enough fat. Doesn't adhere to the principles most LCHF advocates like, but suits me.
When I was gaining weight with LCHF it was probably due to overeating things like nuts and cheese. They are calorie dense.