How to use it
Crunches don't burn the fat over your stomach; overall fat loss does that (food, sleep, total training). Train abs directly anyway, because they're muscles: stronger, thicker abs show sooner and protect your skills (L-sit, levers, flags).
How sure we are
P Evidence: promising. Good studies, but small or few. Use it and keep checking.
Sources
In 24 adults, 6 weeks of ab exercises (5 days a week) didn't change belly fat, waist or body fat, but ab endurance rose from 32 to 47 curl-ups (Vispute et al. 2011, RCT, 🟡) · "abs are partly made in the kitchen": Chris Heria (🟠) · see 393.
Not medical, legal or financial advice.