As I’ve plodded through the first year of my PhD program, I’ve been keeping an eye out for different niches of research that I would like to pursue as an area of interest/expertise. One topic that has grabbed my attention is intermittent fasting (IF). In fact, I am currently preparing a review manuscript to submit to a scientific journal about evidence for or against the health benefits of different forms of fasting.
As a Christian, the topic of fasting is intriguing since it is mentioned a fair amount in the Bible. Fasting is often associated with times of prayer, dependency on God, and decision-making (, , ). In my own life, I have experienced increased feelings of dependency on God during periods of fasting.
“Intermittent fasting” is a broad term that really just means that you periodically do not eat, typically for longer than a normal overnight fast. There are many different types, but I think that popular IF protocols can be grouped into one of three categories: alternate day fasts, daily fasting-feeding splits, and whole day fasts.
Each form of IF utilizes different periods of feeding and fasting. Here is a brief summary of each category:
- Alternate day fasting (ADF) involves alternating between ad libitum (unrestricted) feeding days and fasting days. However, a single meal containing about 25% of normal daily calorie intake is often placed midday on the fasting day. While some individuals do not eat anything on fasting days, most research studies have been conducted using this single meal on fasting days.
- Daily fasting-feeding splits (ie – Warrior Diet® and LeanGains method) involve following the same eating routine each day, with a certain number of hours designated as the fasting window and the remaining hours as the feeding window.
- Warrior Diet® – all calories for a day are consumed in a 4 hour period, meaning that each day involves 20 hours of fasting (this is a 20-4 fasting-feeding split).
- LeanGains – all calories for a day are consumed in an 8 hour period, meaning that each day involves 16 hours of fasting (this is a 16-8 fasting-feeding split). There are other nutritional recommendations associated with this program, but this is the basic layout of the fasting and feeding windows.
- Whole day fasts (ie – Eat Stop Eat) are perhaps the simplest form of IF, and consist of 1-2 days of complete fasting per week plus ad libitum (unrestricted) eating on the other days. Many people utilize this form of IF by eating normally throughout most of the week and then fasting for a 24 hour period on the weekend or at the beginning of the next week.
Currently, there is debate about whether there are unique benefits of fasting or if fasting can simply appear to be effective because it leads to a caloric deficit (due to the decreased amount of time you are eating – if you only eat during certain times, you may not be able to eat as much as you would otherwise). While this is an important question for future studies to examine, I think that some forms of IF can be a useful tool for some people regardless of the answer.
For example, some people find it easier to “eat” or “not eat” rather than restrict their diet every day. Even if following an IF protocol didn’t offer any other benefits (which it may), some individuals may find it an easier, more convenient eating pattern.
Most IF plans don’t tell what to eat, but rather only tell you when to eat. This makes IF plans highly customizable. If you want to eat high-protein, you can still do that. If you want to eat moderate-carbohydrate, you can still do that. If you want to eat less processed food, you can still do that. You get the picture.
This isn’t to say that it doesn’t matter what you eat. Common sense tells us that good nutrition practices should still be followed during an IF-style eating pattern. Research studies haven’t examined much about how macronutrient distribution in the diet affects IF results, but this is a future area of research.
It is also very important to note that not all IF protocols are the same. In fact, some hardly seem like they should fall into a category together at all. Some forms of IF have several research studies that have examined them specifically, but others have a distinct lack of scientific support so far. This isn’t to say that the less-studied protocols are useless – it’s just too early to say. Alternate day fasting is one of the most researched protocols, and you can read more about its benefits here.
In summary, intermittent fasting is an interesting concept that is receiving more attention in society and the scientific community. As Christians, it is particularly interesting because of the potential spiritual and physical aspects involved. More studies are needed that specifically address the routines used by popular programs, as well as examine the health effects of combining these fasting procedures with different forms of exercise (this is the area of research that I am interested in pursuing throughout my doctoral program).
2 While they were worshiping the Lord and fasting, the Holy Spirit said, “Set apart for me Barnabas and Saul for the work to which I have called them.” (ESV)
23 And when they had appointed elders for them in every church, with prayer and fasting they committed them to the Lord in whom they had believed. (ESV)
12 “Yet even now,” declares the Lord,
“return to me with all your heart,
with fasting, with weeping, and with mourning; (ESV)