Intermittent fasting has a variety of meanings... When you don't eat between your evening dinner and your morning breakfast, that's intermittent fasting... The meaning of breakfast is "breaking the fast" (break fast). So if you eat a healthy dinner at, say 6:00 pm and don't eat anything again until 6:00 am, you're practicing intermittent fasting. That's a 12 hour fast and I wouldn't recommend anything longer than that for anyone your age and preferably not that long for your age. I'd suggest a light snack, such as an apple or pear, with peanut butter, etc in the evening... No one wants to go to bed with their tummy growling... It's all dependent on what those meals and snacks include.
I would not recommend fasting during the day, as someone of your age, needs healthy food throughout the day to provide energy for growth and development, as well as energy to play, do sports and other things you do...
You should talk to your parents/guardian about this and make sure they are on board with any weight loss program you decide to start. The first thing you have to determine is if you "really" need to lose weight. You'll also have to make sure you parent's/guardian are willing to provide healthful foods for you to eat at mealtimes and for snacks. It's not always the amount of food you eat, but the types of food you eat, as well, that determine whether you lose, stay the same or gain weight.
Exercise is also key... You have to make sure you get plenty of weight bearing and aerobic exercise in order to build muscle, since muscle helps burn fat faster.
Try to enlist your whole family in your weight loss endeavor; they can be great support and motivation. Be sure to keep posting here to let us know how you're doing and whether or not we can help you...