The simplest thing is not to eat, but if you can't persist, you should eat less. One of my classmates used to eat only apples for three days.

Once a week, I lost 20 pounds in 2 months. See if you can stick to it and lose weight by not eating and exercising.

Standing for half an hour after a meal won't gain weight, but it doesn't have much effect. Keep walking for a period of time every day.