Your grandma sounds mean. She shouldn't laugh at you like that, she should show you support instead of making herself look better by pointing out your faults. Anyway, I doubt that she's perfect! If you have gained weight, you have to figure out why. Do you eat more than you used to? Or have you given up a hobby or sport that used to help keep you fit? Write all the things in your lifestyle that affect your weight, like how many calories and grams of fat you eat a day and then how much exercise you do to balance it. Then think of some changes that you could do every day that would be better, like walking places, going up the stairs and choosing low fat, sugar free foods. Don't be drastic, just make little changes. Those are what counts!