That paper isn't the original- it's a followup. The original is a strict fast (water only) for 72 hours. The FMD (Fasting Mimic Diet) is for 120 hours (5 days)

That paper isn't the original- it's a followup. The original is a strict fast (water only) for 72 hours. The FMD (Fasting Mimic Diet) is for 120 hours (5 days) and has more food allowed: "The human FMD diet consists of a 5 day regimen: day 1 of the diet supplies
1,090 kcal (10% protein, 56% fat, 34% carbohydrate), days 2–5 are identical in formulation and provide 725 kcal (9% protein, 44% fat, 47% carbohydrate)."