The body is homoeostatic and will try to repel any change in body composition and weight. While it is also correct that different people have different metabolism and gut flora that affects our calorie conversion from different foods, the answer is yes. If you count your calories reliably, you can reliably lose weight by adjusting your calorie intake to match your body. If you throw out your body's own function of regulating its weight by measuring your food, you can accurately predict what you'll weigh in, for example, five months. It does not take years.

Noteworthy however is that with change to body composition, your TDEE (known as the amount of calories your body needs to maintain its current weight) changes. However it can easily be accounted for when losing (or gaining as may be the desired outcome for some people) in a controlled way.

Regarding the different metabolism thing: https://examine.com/faq/does-metabolism-vary-between-two-peo... (To asnwer the link's question: Yes. 600 at most calories if you compare two outliers.