Starving the cancer cells by depriving them of sugar and processed carbs may be one of the promising ways to fight this disease that is loved by big pharma, hospitals and insurance industry alike.
Listen carefully, this doesn't mean that ketogenic diet is the silver bullet that would cure "ALL" cancer, however, it could be a powerful preventive tool as well as a cure if used in conjunction with other treatments!!
So DO NOT DISCOUNT THE MEDICAL ADVICE!
Also note, not all cancers use the sugar for energy.
All that said, if you are healthy (or not) try to eat unprocessed whole foods. Moderate Protein, Lots of vegetables, Fruits to get your other micronutrients.
Lots of Water.
Get a balanced diet, Reduce intake of sugars in any and all forms.
Fast occasionally, or Intermittent Fast Daily.
That is how you remain happy, healthy and hopefully be able to prevent cancer.