In Matthew chapter four, we read about Jesus’ temptation by Satan in the wilderness. The text says that Jesus “fasted forty days and forty nights.” How could Jesus possibly live that long without eating? Does the length of Jesus’ fast cast doubt on the reliability of the Bible?
As is always the case, a deeper study of this allegation vindicates Scripture. First keep in mind, while one might assume that biblical fasting always means to abstain from food and drink, a study of examples of fasting in Scripture reveals that there are various types of fasting1
The “Absolute Fast,” where an individual abstains from both food and water. While this kind of fast is mentioned several times in Scripture (e.g., Jonah 3:7; Zechariah 7:5-6; Luke 5:33; Acts 9:9), it was carried out over relatively short periods of time—presumably less than three days (Esther 4:16; Ezra 10:6-10). In rare cases in Scripture, an absolute fast lasted for longer periods of time, wherein the individual could only have survived with supernatural assistance (Exodus 34:28; Deuteronomy 9:9; 1 Kings 19:1-8). However, in those cases, assistance from God is reasonably implied by the text.
The “Partial Fast,” where one’s diet is restricted, rather than complete abstinence occurring (Daniel 1:8,12; 10:3).
The “Normal Fast,” where an individual abstains only from solid food, but not water, for a period of time (2 Samuel 12:16-20; Joel 1:14-16). [Note: the Hebrew term for fast (tsuwm) literally means “to abstain from food.”2]
In what form of fasting did Jesus engage? It is possible that Jesus was supernaturally sustained throughout His fast. In his comments on Matthew 4:2, J.W. McGarvey argued that Jesus’ temptation fast was an example of a supernatural fast, arguing that the phrase, “afterward He was hungry” “implies that his appetite was miraculously suspended during the forty days.”3 In other words, He was not hungry during the 40 days and nights, but was hungry “afterward.”4 Since the Spirit is mentioned as being involved in the temptation period (Matthew 4:1; Luke 4:1), it is not unreasonable to suppose miraculous activity was involved,5 for the same reason that we would suppose Moses was supernaturally sustained by God on Mount Sinai in Exodus 34:28 for “forty days and forty nights” without his eating or drinking.6 While the suggestion that a miracle saved Jesus would be unpalatable to non-Bible believers, Scripture is saturated with examples of supernatural activity (and, indeed, science demands that supernatural activity has happened many times in the past7).8 Since Scripture has divine characteristics that prove it to be from God (the Bible itself is an example of a miracle),9 when it records miraculous occurrences, we know that they happened.
It is probable that Jesus’ fast was a “Normal Fast.”10 If that is true, is it reasonable to suppose that Jesus could have survived for 40 days without food? 11 While a person could only survive without water for a week in “comfortable surroundings,”12 documented cases of people surviving for 40 days (and longer) with water but no food exist,13 with body weight (especially fat content), genetic makeup, gender, and age affecting survival times.14 Dr. Peter Janiszewski wrote: “Generally, it appears as though humans can survive without any food for 30-40 days, as long as they are properly hydrated. Severe symptoms of starvation begin around 35-40 days, and as highlighted by the hunger strikers of the Maze Prison in Belfast in the 1980s, death can occur at around 45-61 days.”15 One of the most remarkable fasts was undertaken by Terence MacSwiney. In a hunger strike, MacSwiney went more than two months without food, dying of starvation after 74 days.16
How is that possible for the human body to go so long without food? One reason is that the body was designed with the ability to adjust its metabolism when energy is scarce.17 After your body converts its food into glucose and its glucose supply is exhausted (within 24 hours), your body begins accessing energy in different ways. First the liver is stimulated to make more glucose. After two-to-three days, fat tissues become the main energy source, and finally, your body enters into ketosis, where fatty acids are used by the liver to form ketones which fuel the brain. After fatty acids in the body have been depleted, the body switches to muscle protein as its main energy source, until the muscles in the body (including the heart) have been depleted.18 Again, the length of time that this process takes hinges on many factors. It is ironic that the most up-to-date research puts the general limit of fasts at 30-40 days. Thus, not only is there nothing about the 40-day fast of Christ that calls into question the Bible’s accuracy, but it actually coincides perfectly with modern research, adding yet another piece of evidence of the Bible’s truthfulness.
1 Andrew Robert Fausset (1878), “Definition for ‘Fasting’ Fausset’s Bible Dictionary,” bible-history.com, https://www.bible-history.com/faussets/f/fasting/; “Fast” (1956), International Standard Bible Encyclopedia, ed. James Orr (Grand Rapids, MI: Eerdmans), 2:1099.
2 F. Brown, S. Driver, and C. Briggs (1906), The Brown-Driver-Briggs Hebrew and English Lexicon (Peabody, MA: Hendrickson), p. 847; Although, the term “food” sometimes includes drink.
3 He cites Exodus 34:28 and 1 Kings 19:1-8 as other similar examples [J.W. McGarvey (2007), A Commentary on Matthew and Mark, Wordsearch Corp].
4 See also Robert Jamieson, A.R. Fausset, and David Brown (2012), Jamieson, Fausset, and Brown Commentary, Wordsearch Corp, Matthew 4:2.
5 Although, granted, supernatural assistance with Jesus’ hunger would lessen the significance of Jesus’ fast and possibly even the Devil’s first temptation.
6 Whatever the meaning of “fast,” Albert Barnes cites Luke 4:2 and notes that Jesus completely abstained from eating food, whether solid food or solid and liquid food [Albert Barnes (2014), Barnes’ Notes on the New Testament, Wordsearch Bible, Matthew 4:2].
7 Cf. Jeff Miller (2017), Science vs. Evolution (Montgomery, AL: Apologetics Press), second edition.
8 While the Bible is replete with examples of miraculous activity, Scripture teaches that such miraculous activity no longer occurs today [Dave Miller (2020), Modern-Day Miracles? Do Miracles, Tongue Speaking, & Holy Spirit Baptism Occur Today? (Montgomery, AL: Apologetics Press), https://store.apologeticspress.org/products/modern-day-miracles].
9 Cf. Kyle Butt (2007), Behold! The Word of God (Montgomery, AL: Apologetics Press).
10 Cf. Fausset; Lauren Sanchez (2020), “What Exactly Is Fasting All About?” BibleStudyTools.com, January 11, https://www.biblestudytools.com/bible-study/topical-studies/what-exactly-is-fasting-all-about.html.
11 While one might assume that the terms “hungry” (Matthew 4:2) and “ate” (Luke 4:2) imply that Jesus’ fast only involved solid food, those terms can occasionally include drinks as their objects as well [See “ἐσθίω” in Frederick William Danker (2014), A Greek-English Lexicon of the New Testament and Other Early Christian Literature, Wordsearch].
12 Randall K. Packer (2002), “How Long Can the Average Person Survive Without Water?” Scientific American on-line, December 9, https://www.scientificamerican.com/article/how-long-can-the-average/.
13 E.g., Michael Peel (1997), “Hunger Strikes,” The British Medical Journal (BMJ), 315:829-830, October 4; Pia Kottusch, Miriam Tillmann, Klaus Puschel (2009), “Survival Time Without Food and Drink,” Archiv Fur Kriminologie, 224[5-6]:184-191, November-December.
14 Alan D. Lieberson (2004), “How Long Can a Person Survive without Food?” Scientific American On-line, November 8, https://www.scientificamerican.com/article/how-long-can-a-person-survive-without-food/; Angela Morrow (2020), “How Long Can You Live Without Food?” VeryWellHealth.com, August 27, https://www.verywellhealth.com/the-decision-to-stop-eating-at-the-end-of-life-1132033#citation-5.
15 Peter Janiszewski (2015), “How Long Can Humans Survive Without Food and Water,” Medical Express, https://medicalxpress.com/news/2015-12-humans-survive-food.html#:~:text=Generally%2C%20it%20appears%20as%20though, around%2045%20to%2061%20days.
16 “Life Mask of Terence MacSwiney” (2020), National Museum of Ireland, https://www.museum.ie/en-IE/Collections-Research/Collection/Resilience/Artefact/Test-2-(1)/578353a6-a33d-49a9-9315-d735d37948f6; “In the last few days of MacSwiney’s strike, far too late to make any difference, the government began force-feeding MacSwiney” [Jason Perlman (2007), “Terence MacSwiney: The Triumph and Tragedy of the Hunger Strike,” New York History, 88, The New York State Historical Association, https://web.archive.org/web/20081204101849/http://www.historycooperative.org/journals/nyh/88.3/perlman.html].
18 Morrow; M.L. Steinhauser, et al. (2018), “The Circulating Metabolome of Human Starvation,” JCI Insight, 3:e121434, August 23.