Chapter 19 offers advice about what to eat. Fung explains that all diets work in the beginning, but that they eventually fail because the body activates mechanisms to return to its set weight: Lost pounds come back as the metabolism slows and hunger increases. Like heart disease and cancer, obesity is a multifactorial disease. Calories, carbohydrates, insulin resistance, and sugar contribute to weight gain while fiber offers some protection. Of these factors, insulin is the most important. Most diets only address one part of the obesity problem while ignoring others. By contrast, Fung emphasizes the overlapping pathways that result in obesity, all of which relate to a hormonal imbalance, namely, high insulin levels. Patients with insulin resistance might benefit from fasting, while a diet low in refined carbohydrates may be more appropriate for those with high blood glucose levels. For others, increasing dietary fiber and reducing stress (and therefore cortisol) may be effective. For long-term success, doctors must treat different facets of the disease with diet, medication, and stress reduction.

Fung makes the following recommendations to treat obesity:

1) Reduce added sugars to lower blood glucose levels and insulin resistance.