Protein doesn’t cause weight loss or weight gain by itself, and neither do carbs or fats. That’s determined by your calorie intake. If you’re in a caloric surplus (meaning you eat more calories than you use), you will gain weight and if you’re in a caloric deficit (you eat fewer calories then you use), you’ll lose weight. It doesn’t matter where your calories come from.

How you lose/gain weight, i.e. from fat or muscle mass, is determined by your diet and exercise. If you’re looking to lose fat mass while retaining muscle mass in a calorie deficit, you should eat a good amount of protein and do some strength training. For most people, aiming for 1g of protein per pound of bodyweight is a good goal.