Too much fat in your diet will stall your weight loss. Even if you are fat adapted or in ketosis, your body will still give preference to dietary fat to produce energy or ketones, before starting utilizing the fat stored in your adipocytes (fat cells).
It’s more efficient to oxydize the fatty acids already in the bloodstream than the one store in our adipose tissue, that’s why if you want to lose weight you have to reduce the amount of fat that you eat, even if you are in ketosis.
The “fat burns fat” paradigm is obviously wrong, and it’s due to an oversimplification of the concept that “a calorie isn’t a calorie”. Our metabolism is much more complex in using macro nutrients as a source of energy than a calorimeter (the instrument used to measure the amount of calories in fats, carbs and proteins), but the amount of fat that you eat can and will stall your fat loss or even make you fatter if excessive.
Now, back to dietary fat versus stored fat. Once the fat eaten with your diet is used, our body will start mobilizing the fatty acids in our adipose tissue, If you eat less fat than the you need for energy purpose, you’ll lose weight.
That’s why it’s so important to limit or avoid completely snacks and fat bombs if you are trying to lose weight, and that’s actually one of the benefits of eating higher quantities of fat compared to a low fat diet: you can easily go from meal to meal without being hungry and without the constant need of snacking.
The same thing applies to exogenous ketones, a category of product that can have some effective use in elite athletes to improve performances, but that are completely useless for weight loss and can actually reduce it: more ketones in your bloodstream means less fat mobilization from fat tissue.
In short, eat less than 20-25 grams of carbs per day, eat approximately 2 grams of protein per kg of ideal body weight per day, and then increase or decrease the fats in your diet depending on what goal you are aiming for, weight loss or muscle gain.