Conditional sentences are composed of 2 parts (a cause part and a result part).
Up till now we looked at sentence constructions: cause ..... result.
However,, it is possible to flip this around:
"Your belly will be flatter if you exercise regularly"
"Your belly will be flatter" = result
"If you exercise regularly" = cause
We see the construction IF + present simple .... will +verb
Your belly will be flatter if you exercise regularly