Calorie deficit doesn't work. One has to switch body to burning fat and eating any carbs prevents it due to keeping carb metabolism pathway instead of fat-burning one, switching body to starvation mode, depression and major muscle loss. The fastest way to lose fat weight is electrolyte fasting with no food (1lb/0.5kg weight loss a day). This method works for very determined fairly healthy folks but most aren't those; it's also super important to drink a lot during this fasting and break the fast by taking high-dose thiamine. Carnivore diet (meat/fish/quality fat) gives similar results due to activating the same metabolic pathway while keeping eating but the rate of weight loss is more like 2lb/1kg a week and not feeling hungry at all.