I REALLY do believe that lifting heavy weights is crucial to actually and significantly increasing bone density and food and supplements only are not enough.
Food and supplements were enough for me. My spine collapsed in my late 20s due to advanced osteoporosis from undiagnosed and untreated Hashimoto’s Disease. I sustained 12 vertebral fractures, 8 of which compressed, and I had to learn how to walk again. I could barely lift my body, let alone lift weights, and I managed to improved my DEXA score from -6.7 to -3.6 within a year of my doctor putting me on a Weston A. Price Foundation inspired diet supplemented with cod liver oil.