Is there an effective way to lose belly fat in a short period of time?

In the past, even if I went hungry just a little

It felt like my stomach was shrinking quickly.

These days, even if you diet for a week...

It seems like there is almost no change.

I am currently eating almost one meal a day.

50 minutes of power walking as aerobic exercise.

I've been riding an indoor bike for 30 minutes.

Maybe it's because I've gotten too used to the routine

It's because there haven't been any major changes in my body.

What can be added here

Please recommend some aerobic or anaerobic exercises.