"Huge problem", eh?
Please describe how the natural diet of the hunter-gatherer homo sapiens (circa 100,000 BC) was "balanced" before the introduction of organized agriculture (circa 9,000 BC).
And what are those human canines and incisors for? Chewing tomatos and grass? What's that big brain for? Chasing down a wild thistle?
What was the average lifespan before and after?
Health is what matters, and it has two aspects that are improtant to me.
(1)length of life
(2)the physical condition to do whatever activity I feel like doing whenever I feel like doing it wihtout worrying about my physical condition.
Aspect 2 is far more important to me than 1. I have absolutely no intention of spending the last 20 years of a long life sitting in a wheelchair drooling on myself.
There is probably no greater physical limitation than serious overweight (say, 40 pounds overweight or more). If a diet works to help someone get rid of this limitation, what difference does it make whether it's 'balanced' or not? If they lose a few years of longevity and gain the opportunity to live fully, they come out ahead, IMO.