I know a woman that has had a very strict organic diet with lots of veggies for 20+ years... she's on her second round with cancer!! She's in good shape for walking distances and all but she has the cancer, that pretty much cancels every other benefit of her diet...
There's anecdotal evidence, that white caucasian's (full of tinned, salted etc foods-may have been a war thing) didn't rot down in the jungles of Papua New Guineau at anywhere near the rate of native's, who had a still primitive/truly organic diet.
If you go on a calorie restricted diet and lost weight and if you record your calorie intake daily and your weight loss daily, you can calculate
your maximum calorie intake to maintain a specific weight.
I did that years ago and it still works. My maximum calorie intake to
maintain 150 lbs is 1700 calories per day.