First of all, it is basically impossible for you to do so. One meal a day is not good for your health, you can't lose weight, and you are easy to get sick. Especially anorexia, dysmenorrhea and irregular menstruation.

You can do it this way.

Three meals a day are essential, and the most important thing is breakfast and lunch. Breakfast can be milk and toast to ensure carbohydrate intake.

Lunch should be white meat+vegetables+rice, supplemented with fiber and protein. Don't want to eat meat, tofu and soybeans are good supplements for protein.

You can have porridge for dinner.

Exercise doesn't need many tricks. Jogging is aerobic exercise. Considering the environmental problems, it can be played at night and after meals.

Mainly skipping rope, jumping for half an hour at a time, without interruption. At first 10 minutes, and then increase every day. But it won't take more than half an hour.

You persisted in this way 1 month. Every day, it is estimated that you will soon find yourself thin. Usually cucumbers and tomatoes are snacks.