Is a calorie a calorie regardless of what kind of food it is?

Hello.

For instance, if a person decides to go on a 1500 calorie per day diet. If three pieces of cheese pizza are eaten for this day, each 500 calories. The person eats nothing else - so the calorie limit of 1500 is adhered to. Or, say that person eats 1500 calories a day of salads, fruits, etc. - healthy foods. Will the weight loss (all other considerations being equal) be the same? Regardless of the source of the calories? I'd like to know. Thank you.