Most effective exercise to lose belly fat?

Any. Exercise in general, coupled w/ diet, helps you lose belly fat. A combo of too much of the wrong kinds of carbs & not enough active muscle tissue is what sets up belly fat. It's added to by age, hormones & stress. Spot reducing exercise can make belly muscles stronger & shapelier, but you won't see them until the calories come down & your other muscles are toned & gobbling up glucose.

Related Questions

What do you think is the most effective exercise to lose belly fat?

No preferential loss. There is not a non-surgical approach to preferentially remove fat from one part of the body. Read more...
Target abd muscles. Avoid sugary drinks including use of sugar substitutes, balanced diet with slight preference to lean protein. Excercise that strenghten abd muscles and overall weight loss. Read more...