Denial is beneficial for the soul while starvation is effective against desire (nafs). Starvation is also known to be beneficial to the body. It is known that animals fed near-starvation diet see dramatic boosts in their lifespans.
The lack of nutrition seems to make our cellular repair mechanism work harder. [Maybe to their full capacity and true potential(?) I'm no doctor]. The cellular repair mechanism helps to slow the gradual accumulation of cellular damage that is related to aging. In time of scarcity, normal cells switch their attention away from
reproduction and towards preservation, beefing up their repair
mechanisms. We have been pampering our body with numerous supplements and medicine that it might become "complacent" in the future.
It is now found that fasting is helpful in treating tumor since it both protect healthy tissue and make tumors easier to treat. Furthermore, it is found that fasting can actually make cancerous cells more susceptible to
chemotherapy than they otherwise might be (experiment done on mice). Cancerous mice treated with a
combination of chemotherapy and fasting had better survival chances and
smaller tumors, for several different types of cancer, than those
treated with either fasting or chemotherapy alone. Fasting is cheap, affordable, safe and, in theory, should work against a wide variety of cancer types.
Lack of nutrients seems to spur the activity of cellular repair mechanisms. Maybe our body knows best and is created in a way to respond naturally in accordance with situations. That might be why we often don't feel like eating when we are ill. I believe this is also for medicine and supplements. The less we depend on them, the better of our immune system would be. Human used to live for hundreds of years without the help of modern medicine. However, they also benefited from the less/non-polluted environment around them.