It doesnt sound like your mindset is so healthy at all, and there are many thoghts and fears you need to challenge. Exercise shouldnt be done "just so that you can eat" or to compensate for eating - exercise should be done because you enjoy it, but also you can eat even if you dont exercise, you dont need to compensate or eat less. The reason you might be feeling so hungry is 1) When you are studying your brain uses alot of energy to concentrate and focus and you feel more hungry, 2) You feel more stressed which can increase hunger, 3) Your body so desperatly wants more food and calories and to reach its healthy weight (DONT focus on numbers, Jjust because you have set your goal weight at X kg doesnt mean that your body will settle there. So allow your body to settle where it wants and dont focus on a number). 4) Exercise can actually surpress appetite, so now when you exercise less your true hunger is coming and you should listen to that hunger.
You shouldnt walk around feeling super hungry, then you wont be able to study or concentrate or do anything because you will just think about food and how hungry you are. So my best suggestion is to make sure you are satisfied after every meal. DOESNT MATTER how much you need to eat... doesnt matter if you need to eat 3 portions of oatmeal in the morning or 3 portions of pasta in the evening - eat until you are full. Also healthy fats are essential in your diet but also they help fill you up. Fats dont make you fat. You need healthy fats in your diet and i can assure you that if you add fat into your daily intake it will help keep you fuller and more satisfied! Add some nuts or nut butter to your oatmeal, add oil to your food or avocado on toast or to your salad, add seeds and nuts to your snacks. Your fear of fats is something you need to overcome and face, whether you do it this week, next month or 3 years from now you cant fully recover unless you face that fear as it is holding you back in life. Ask yourself, why do fats scare you and are those thoughts logical? What will happen if you eat healthy fats? What are you scared will happen? Slowly add them back into your diet, maybe start with adding 1 tablespoon of nut butter to your oatmeal in the morning or adding butter on your bread. .Small steps will make a difference.