If you eat to the caloric target set by some app, it is highly likely that you are not eating enough. Eat too little food, and your metabolism will eventually slow down to compensate. This is why people never lose as much weight as they are supposed to by cutting calories. Eat more food, and the metabolism speeds up.
Naturally, there are limits. If we really eat too little, we die of starvation. Too much, and eventually we will start storing energy in the form of fat. But within quite a broad range, the body can adjust.
So if you are satisfied with only 1300 calories, the question becomes whether or not you have slowed your metabolic rate (the Biggest Loser contestants appear to have permanently reduced their metabolic rates, which hampers their efforts to lose the weight they regained after leaving the show). In that case, you can try something called “reverse dieting” to see if you can slowly raise your metabolic rate, but that takes time. If you are eating 1300 calories for no other reason than because the app told you to, then try eating enough at mealtime to satisfy your hunger. That may be a large quantity of food at first, but you will likely experience a sudden drop in appetite, which is when your hormones finally start working properly.
There are a number of people on these forums who will tell you that their hormones are “broken” and there is no limit to the amount of food they eat if they don’t stop themselves; they never stop being hungry. All I can say is that over time it will become clear to you whether or not you are part of that group, and at that point you can deal with it. In the meantime, however, keep eating enough food to satisfy your hunger, and see where it leads. Many other forum members have reported that their fat loss didn’t begin until they started eating more, not less.