It is not uncommon to experience rapid weight loss within the first few days to week of starting Keto. However, much of this weight lost is in the form of water as your body is adjusting to the change to low carbohydrate intake.
The timeline for experiencing fat loss is different for everyone. It is important to note that you are likely experiencing some degree of fat loss very early on in Keto, even during the water loss phase of the diet. However, you will likely find that after 3-4 weeks that fat loss becomes more noticeable!