You haven't exercised for a long time, and now you are heavier. I suggest you do some aerobic exercise for a long time to improve your heart and lung function, such as brisk walking and brisk walking, with a small amount of exercise but a long time. To keep yourself in a state where you can control your breathing with your nose, but your breathing is tight, it is best to persist for more than 40 minutes, and then you will generally sweat. After getting used to it for a while, you can increase the amount of exercise or extend the time.

However, if you want to improve your long-distance running performance, you'd better lose weight. Diet control is a good way. You also need to control your diet and lose weight through aerobic exercise, because a bottle of coke will waste 40 minutes of jogging. When your weight is reduced to 75 kg, your 1000 meter score will be easily improved by 30 seconds or more (I personally lost 10kg in one semester by controlling my diet), and I can lift one kilometer for nearly one minute without special exercise). Instead of not eating, it is better to supplement sugar and protein appropriately, and replace the steamed bread, rice and meat that used to make you full with vegetables and fruits.

Fitness needs to be done step by step, and diet control also needs science, so as not to affect study and life.