^DeBruyne L, Pinna K, Whitney E (2011). "Chapter 7: Nutrition in practice — Fad Diets". Nutrition and Diet Therapy. Cengage Learning. p. 209. ISBN978-1-133-71550-4. "a fad diet by any other name would still be a fad diet." And the names are legion: the Atkins Diet, the Cheater's Diet, the South Beach Diet, the Zone Diet. Year after year, "new and improved" diets appear ...
^Cataldo, Corrine Balog; DeBruyne, Linda Kelly; Whitney, Eleanor Noss. (1999). Nutrition and Diet Therapy: Principles and Practice. West/Wadsworth. p. 214. ISBN978-0534546014 "Most fad diets, including the currently popular Zone Diet, advocate essentially the same high-protein, low- carbohydrate diet... Long-term use of such diets may produce adverse side effects such as nausea, fatigue, constipation, and low blood pressure."
^Mechanick, Jeffrey I; Brett, Elise M. (2006). Nutritional Strategies for the Diabetic/Prediabetic Patient. CRC Press. p. 96. ISBN9781420014884 "No conclusive clinical studies have been conducted on the Zone Diet and, at present, it remains a fad diet without any scientific merit."