During a 40-day fast the body passes through five stages

Dr. Lee "Last time we noted that for a man 175 cm tall and 70 kg, roughly 13.5 kg of lipid is stored in the body. If we stop eating and use those stored lipids as our energy source, how many grams would we need to use per day? Let's imagine a simple hibernation. Ground squirrels, after all, hibernate for as long as five months. Imagine a human doing the same."

Zoe "I'll calculate. Lipid yields 9 kcal per gram. If basal metabolism is 1,800 kcal per day, then about 200 g of lipid per day would suffice."

Dr. Lee "Ha — Zoe, you're quick at arithmetic. Yes — 200 g of lipid per day is enough to handle a day's activity."

Grace "If 13.5 kg of lipid is stored, and 200 g — that is, 0.2 kg — is enough per day, then on lipid alone we could live for over 70 days."

Dr. Lee "Yes. Anyone in reasonably good health can live well without food for around 40 days. Do any of you happen to know how long Jesus fasted, in scripture?"

Grace "I do — I've read the Bible more than 20 times. He fasted for 40 days, and then began his public ministry."