Consider the following: 1500 calories worth of Snickers bar would not have the same effects as 1500 calories worth of beans and legumes or 1500 calories of pure soda. Satiety, nutrient and calorie availability, hormones (insulin), all differ depending on what you're eating -- and how often and how much you're eating. Even the combination of macro nutrients will have different effects: for example, fats + simple carbs is way worse than fats + proteins + fiber.
And exercise, mood, sunshine also factor in.
In the end, of course, thermodynamics holds and if you eat 1000 calories (no matter what form they take) when you need at a minimum 1500 then 100% yoi will lose weight. But how fast, how easy or how healthy that would be is a different story depending on what you're eating.