Updated: Oct 25, 2019
Post Written by Josh Elsesser
Intermittent Fasting (IF) is the name some scientists give to the practice of occasionally going for long periods of time without eating. If you think that sounds horrible, wait a second. We all do IF every day. It’s called sleeping. The reason the first meal of the day is called breakfast is because you are literally breaking your fast.
In fact humans have done various forms of IF for thousands of years. The traditional sleep cycle, longer periods of food scarcity, and for religious reasons such as Ramadan or the LDS Fast Sunday.
There have been many studies done on IF as well reporting many benefits such as:
blood lipids - including decreased triglycerides and LDL
blood pressure - perhaps through changes in sympathetic/parasympathetic activity
markers of inflammation - including CRP, IL-6, TNF, BDNF, and more
oxidative stress - using markers of protein, lipid, and DNA damage
risk of cancer - through a host of proposed mechanisms
cellular turnover and repair - called autophagocytosis
fat burning - increase in fatty acid oxidation later in the fast
growth hormone release later in the fast (hormonally mediated)
metabolic rate later in the fast (stimulated by epinephrine and norepinephrine release)
appetite control - perhaps through changes in PPY and ghrelin
blood sugar control - by lowering blood glucose and increasing insulin sensitivity
cardiovascular function - by offering protection against ischemic injury to the heart
effectiveness of chemotherapy - by allowing for higher doses more frequently
neurogenesis and neuronal plasticity - by offering protection against neurotoxins
With all of these benefits, you are probably thinking “sign me up!” If you are interested in trying IF here are the 5 most common ways IF is used.
1. Alternate Day Fasting (36 hr fast/12 hr feed) With this plan you simply eat every other day. So on Monday, you’d eat within a 12-hour window, say, 8 AM to 8 PM. Then you’d fast overnight on Monday, and all day/overnight on Tuesday. You’d eat again from 8 AM to 8 PM on Wednesday. And so on. Alternate day fasters are encouraged to make good eating choices, but they’re allowed to eat what they want on the non-fasting days.
2. Meal-skipping (Random)
Some IF proponents believe we should behave like our evolutionary ancestors did. As humans evolved to get their food and exercise randomly, so should we. This brand of IF includes eating unprocessed “evolutionary friendly” food (think Paleo-diet type), randomly cycling daily calorie intake, and randomly skipping a breakfast or dinner meal once or twice a week. The rules are very flexible. (It is random, after all.)
3. Eat Stop Eat (24 hour fast, 1 or 2 times per week)
On this plan, you fast for a full 24 hours once or twice per week, eating sensibly (higher protein, minimizing processed foods, etc.) the rest of the week. It’s flexible: You can choose whichever 24 hours you want. Want to fast from breakfast to breakfast? That’s cool. Just eat breakfast on Monday, and don’t eat again until breakfast on Tuesday. Want to fast dinner to dinner? That’s cool too. Eat dinner on Wednesday, and don’t eat again until dinner on Thursday.
4. Lean Gains (16h fast / 8h feed)
This brand of fasting is based on an 8-hour feeding period followed by a 16-hour fast. However, it also layers a few other food rules on top. The diet should be high in protein, should cycle carbohydrates, should include fasted training, and should use nutrient timing (eating the bulk of your calories during the post-exercise period). On this plan, you fast from, say, 9 PM on Monday night until 1 PM on Tuesday afternoon. If you’re going to exercise, you’d do so just before 1 PM on Tuesday, with 10 g BCAAs (branched chain amino acids) during training. After training, you eat 2-3 meals before 9 PM, with your biggest meal coming right after exercise. The fast begins again on Tuesday evening until Wednesday at 1 PM, and repeats every day.
5. Warrior Diet (20 hour fast / 4 hour feed)
On this plan, you would either fast, or eat very small amounts of specifically recommended foods, for the first 18-20 hours of each day, working out during this period of under eating. Then, you would eat the majority of your daily intake within a 4-6 hour over feeding window. After that 4-6 hour over feeding period, you would repeat the under eating/fasting for the next 18-20 hours. Generally, most people place their over feeding window at the end of the day, as it’s more convenient for family dinners and after-work training sessions. However, modifications can be made based on individual and scheduling differences.
The one I have recommended to clients that are interested in trying IF is the Lean Gains, or as I refer to it as the 16/8 plan. The 16/8 protocol is based on a few simple rules:
Fast 16 hours every day. (this is called for your fasting interval)
Eat within an 8-hour window every day. (this is called your feeding interval)
Exercise with high intensity, a few times per week, often while still in a fasted state.
Use 10 g of BCAA before or during your exercise session.
On your exercise days, eat 2-3 BIG meals of protein (meat), veggies, and carbs.
Eat your largest meal directly after your workout.
On non-exercise days, eat 2-3 meals of protein (meat), veggies, and fats.
Eat mostly whole, minimally processed foods, instead of processed foods or supplements.
So have fun. Experiment with yourself. If you do, keep a detailed journal of:
What you ate and when
What your exercise was
How you felt: energy, brain fog, mood