Can you lose weight by eating one meal a day?
Eating one meal a day is a lifestyle change of getting into Intermittent Fasting (IF). People follow different schedules of IF, which not necessarily mean one meal a day. The most common schedules are 16/8, 20/4 and 24/0. In 16/8, eat all your meals within an 8 hour window and fast for 16 hours. Most people eat (rather drink) zero carb during the 16 hours fasting window in the form of one or two bullet proof coffee or club soda with salt or green tea. In 20/4 schedule, all meals are eaten within a 4 hour window. 24/0 schedule is the one you have asked as one meal at every 24 hours.
It takes some time to get used to the schedule one follows. Once used to the schedule, it is easy to follow as body is adapted to ketones (fat) as energy source rather than glycogen (sugar) as energy source. While in ketogenic state, the IF person does not feel hungry except at the scheduled time. Generally it is difficult to eat the entire day's calorie requirement in a single meal of the day. So people end up eating below their BMR requirements in 24/0 schedule, which leads to weight loss or slower metabolism. But it is possible to meet BMR calorie needs in 16/8 and 20/4 schedules.