How often should we fast?

fastingSince we are now in Lent, it might be a good time to review the spiritual habit of fasting. Jesus clearly expected his followers to fast after he had gone, so it is odd that this is not a widespread habit amongst all Christians. To answer this, we need to ask some background questions. How often did the first Jesus-followers fast? Was it an occasional thing, focused on specific events or causes? Or was it something more habitual and regular, an integral part of their devotional life? And what was its significance?

As most studies of the subject point out, fasting in the Old Testament was associated either with particular festivals (such as the Day of Atonement), with particularly intense experiences (as with Moses spending 40 days in the presence of God on Mount Sinai), or with special seasons or feelings. Typically in the prophets and the writings, fasting is associated either with grieving, repentance, or intense prayer for a particular cause. There is nothing in any of these references to suggest that fasting was a habitual part of regular devotional activity.

But there are some fascinating clues to a change of perspective in the (so-called) inter-testamental period. The Book of Tobit relates stories set in the eighth century BC, but most believe it was written in the mid-second century BC (most scholars date the book of Daniel to a similar period).

Tobit 12.8–10 records the teaching of an angel as follows (in the style of sayings from Wisdom literature):




What is striking here, in relation to the earlier Old Testament texts, is that fasting has now become a regular part of devotional activity. What is even more striking is the close relationship between the practices in this text and Jesus’ teaching in Matt 6.1–18:

Be careful not to do your ‘acts of righteousness’ in front of others, to be seen by them… So when you give to the needy, do not announce it with trumpets… And when you pray, do not be like the hypocrites… When you fast, do not look somber as the hypocrites do…

Here we have the same cluster of concerns—of righteousness, prayer, almsgiving, and fasting. And, once again, fasting is assumed to be a regular, habitual part of the devotional life, not something reserved for special occasions. This also fits with the question that is asked of Jesus and his disciples:

How is it that John’s disciples and the disciples of the Pharisees are fasting, but yours are not? (Mark 2.18).

The TNIV has translated this in a way suggesting this was a continual practice—and for good reason. In the parallel in Luke 5.33, the question appears to be on the lips of Jesus’ critics who state:

John’s disciples often [Gk: pukna, frequently] fast and pray, and so do the disciples of the Pharisees, but yours go on eating and drinking.

Matthew appears to be caught between Mark and Luke. Whilst most manuscripts have at Matt 9.14 John’s disciples asking the question ‘How is it that we and the Pharisees fast…?’, a minority tradition has added the word ‘often’ [Gk polla], probably in an attempt to harmonise Matthew with Luke.

didache-largeIn fact, Luke appears to have a particular interest in this regular habit. In Jesus’ story of the Pharisee and the tax collector in Luke 18, we hear the Pharisee proclaim, ‘I fast twice a week…’ (Luke 18.12), and in fact we know on which days he fasted! An early Christian teaching document, the Didache (usually dated to the late first century, but lost until its rediscovery in the 19th) says this:

Chapter 8: But let not your fasts be with the hypocrites, for they fast on the second and fifth day of the week. Rather, fast on the fourth day and the Preparation (Friday). Do not pray like the hypocrites, but rather as the Lord commanded in his Gospel, like this:…

and then follows a version of the Lord’s prayer very similar to the one we find in Matthew (‘his Gospel’). (For more on this, see the post on Jesus’ poetic teaching.) The term ‘hypocrites’ most likely refers to Jews who do not follow Jesus (hence almost certainly dating the Didache to some time after the year 85) but who fast—guess what!—on two days a week, Mondays and Thursdays. And precisely in line with Jesus teaching in all three Synoptic gospels, the followers of Jesus are also expected to fast two days a week, albeit on different days. In one of Luke’s other references to this practice, Acts 13.2, again it appears to be a habitual practice of the community of believers. (There is evidence that this regular fasting went from after breakfast until a light evening meal, rather than being a 24-hour period without food.)

Further confirmation of this practice comes from a slightly unlikely source. In Rabbinic Judaism from the second century onwards, there is no evidence that fasting continued to be a habitual practice. Instead, patterns of fasting return to what we find in the Old Testament. The best historical explanation of this is the mirror of what we find in the Didache. Just as the early Jewish followers of Jesus began to define themselves over against mainstream Judaism, so Rabbinical Judaism then began to define itself against the growing Jesus movement. So a practice like regular fasting, which marked out Jesus-followers against their pagan context, would be a good thing to drop.

Finally, it’s worth reflecting on what this habit of fasting two days a week signified as a devotional practice. As Eliezer Diamond notes (Holy Men and Hunger Artists, p 130) the idea of regular fasting would have seemed odd to most in Graeco-Roman culture. The majority would have seen no need for it, whilst certain ascetic groups did practice fasting, but as a sign of detachment from the world. Intermittent fasting says something different. ‘Feast’ days celebrated a world made by God and all the good in it; alongside this, ‘fast’ days signified repentance, mourning and longing for deliverance—just the sort of practice you might adopt if you were awaiting the deliverance of a Messiah and the breaking in of the age to come. Intermittent fasting is just the sort of thing you might continue to practice if you wanted to continue to both affirm the world you lived in, but also to look for an age to come; it is the dietary expression of the ‘now and not yet’ of the kingdom of God (or, to use a theological term, the ‘partially realised eschatology’) we find in the New Testament. In fact, it is just the thing you would do if you were in the habit of praying ‘Your kingdom come, your will be done, on earth as it is in heaven’!mosley_1810279c

(In a wonderful piece of synchronicity, Michael Mosley advocates, on health grounds, intermittent fasting on…Mondays and Thursdays!).

So, this Lent, is there any reason why we should not all adopt this ancient practice of intermittent, twice-weekly fasting, as we look forward not only to the breaking in of the kingdom through Jesus’ cross and resurrection, but the completion of all things in his coming again?






4 thoughts on “How often should we fast?”

  1. Thanks for this Ian, as a runner from a practical point of view I’ve always struggled with the notion of fasting and running. Often after a run you want to take on nutrition to replenish what is stored up at the moment following a run for the next time. So timing of fasting, length of fasting, what to fast has both interested me and also perplexed me.

    But in truth I also like my food, so running without it, or trying to stagger my fasts to fit my runs, always seemed like another layer of complexity and stress I could do without. If I’m being honest its been easier to avoid thinking about, as an excuse to not do it! Perhaps you’ve just prompted me to face that. However on a practical level if there are any other readers who’ve faced the same issue, then I’d love to know what they think, also. Recognising there is no one size fits all. Any practical tips mate, is fasting TV? Social Media? as acceptable as food?

    Thanks as ever


    • Thanks, Dave, that’s interesting. I do recall coming across something in the literature about the benefits of fasting whilst training, and I think some athletes do do this…

      Yes, I think it is possible to *extend* the idea of fasting to other areas of life, hence the popularity of such abstinences during Lent. But I am not convinced that it is a substitute, since food is so fundamental to life as we know it…

    • Hi Dave,
      I’m many seasons later in finding your comment- but I am an athlete currently fasting. It is week one of 4 in a partial fast. I run every day and lift weights as well as dance. For me, I am taking it week by week. I have done some things to ensure my immunity with supplements as well as making sure what I do take in is very nutrient rich. It has actually got me eating very clean. If I feel like I’m going to pass out at work I will sip on juice but try to abstain. And sleep has become so much more necessary. 9 hours to rebuild my muscles.

      I think planning is essential here. I continue to do my workouts- though I may have to lessen them as time goes on-but it’s been really great. I think it is different for athletes- but you really just need to pray about it and walk closely with God in how he wants you to fast.

  2. Eastern Christians (Orthodox) still fast on Wednesdays and Fridays as you read from the Didache. During Lent & Christmas they fast for 40 days, plus another two shorter fasting seasons. I only mention it since you are listing the Didache as a source, and hardly any non Orthodox Christians even believe it’s real, lol. Good job.


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