The simple truth is that if we fix the cells, EVERYTHING else is fixed because the body IS a community of cells. Even the genes inside the cells turn on and off according to their environment (nutrients & energy). It's the cells that take the various building blocks of life (nutrients) and together in a co-operative manner make the body the whole functioning thing that it is. If we don't give the cells what they need, and subject them to what they don't want, the body of course fails at its overall optimal functioning.
When we allow the body to heal ITSELF with proper nutrition and positive peaceful emotions, it's very important to understand that the body can't create an entire body's worth of all new cells in one day. It's called a "degenerative disease" because it developed over time, and because disease doesn't suddenly happen in one day, it doesn't disappear in one day either.
Dieting isn't supposed to be something that one does temporarily. The body requires regular maintenance and care on a daily basis because the body is quite literally made of what nutrients (or lack thereof) that goes into it every single day. "Health is a habit, not an event."
People think they catch a cold or flu because of somebody else that had it, but in actuality, our own immune system was weak and susceptible to that illness because of our own negative lifestyle choices (which are based on unawareness).
Just as giving the cells ALL the nutrients that they need in the first place will prevent disease from happening, giving the cells ALL the nutrients that they need will also cure disease after the fact.