Yes we do. We toss out the technology and go back to substance farming or hunter/gathering. You'll have no trouble "eating less". But that requires social coordination and humans much prefer to escape society through the use of drugs. Always have, always will.
Is it helpful to point out solutions for problems facing society that don't apply to "humans"?
Yes, mass starvation is an extremely effective weight loss technique. However, some feel there are downsides to this approach.
There is an implicit requirement of "while not making survival chances significantly lower".
I think the revolt you'd get from trying to move everyone back to subsistence farming (and also getting conquered by some other group who didn't do this) also means we don't know how to do that successfully. You're ignoring that last word again.