It isn't easy because its based on your body type, weight and type of food you eat. (you could ask your doctor about starting a diet)
although you could go with a basic way:
1. just eat normally but also try to like eat a smaller amount of oily foods
2. start exercising but do the easier ones for you
3. take care of your self
4. i don't know your gender but most girls are really insecure so don't be shy to ask your for parents something or be shy to eat at the table
5. think positive don't worry too much about something and stay on the positive side
6. a healthy mindset can motivate you
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top recommended exercises:
pull ups
sit ups
jogging
and walking