How-to Guide
Fasting
INTRODUCTION
We define fasting as a 'catch-all term for purposely:
- Skipping some type of (previously 'normal') eating occasions.
- Restricting some type of food group throughout the course of a day, week, or month
- Or maintaining a shortened window of time in your day where you consume calories and a longer period of time in your day with no calorie intake.
There are a variety of suggested health and performance-related benefits which include weight loss, blood sugar control, better fat burning, reductions in long term disease-risk, improved mental clarity, and the potential to increase healthspan and longevity. Here we discuss the most established methods of fasting plus tips for implementing fasting successfully.
METHODS OF FASTING
Shortened Eating Window
Shortened eating windows, also known as time-restricted feeding, are when you keep all of your daily food intakes to a window of 8-12 hours/day. Water is fine outside of this window, as it’s really more about caloric intake.
Range: 12 hrs is likely fine for already healthy people, but insulin-resistant and overweight people may need to squeeze that eating window down to 8-10 hrs for the best effect. Anecdotally, males and females may respond differently to shortened eating windows; females may respond better to a longer eating window, for example, 10-12 h of eating rather than 8-10 h.
Rule of thumb: Eat while the sun is out. Try and consume most of your food when you can see the sun in the sky.
Window timing: Earlier hours (e.g. 8 or 9 am to 5 or 6 pm) are generally better than later hours (e.g. noon to 8 pm) but find what works for you in your life and aim to maintain a consistent eating window. Eating in that window most of the time may be good enough! Following this routine 5 days/wk should give you most of the benefit, while still allowing you to eat a bit later on weekends or other times you want to bend your rules some. Generally, stay as consistent as you can.
5:2 Big Days - Little Days
In this approach, you consume about 500 kcals per day (or ~25% of your estimated needs) on two non-consecutive days/week.
Flexibility: This approach allows you to eat more on your normal days and still come out in a caloric deficit at the end of the week!
Choosing wisely: The 500 kcals can be divided any way you’d like, however, the greatest satiety will come from a substantial amount of protein (~50-60g, which is about 7 oz of a lean protein total for the day), plus some vegetables. This will also help to maintain muscle mass and lose fat mass.
Fasting Fridays
A more relaxed but less established version of a big day, little day approach is to choose one day a week to restrict calories.
Consistency: Establishing a set day to fast in advance can help keep your fasting regime consistent as you’re taking the decision-making process out of your weekly routine.
Convenience: One option is to buy pre-made meals for your reduced-calorie fast days. Splendid Spoon offers healthy and delicious soups delivered to you. These ready-to-drink soups are high-nutrient meals that help you feel relatively satiated per calorie, which helps make the fasting days easier to do. Yes, choose your food wisely on your fasting days.
20-24 h Fast
This can be done 1-2x per week or even 1-2x per month.
Choose your period: Breakfast to Breakfast, Lunch to lunch, or dinner to dinner are all options. Dinner to dinner is the most popular. Eat a large early dinner or late lunch, which can hold you through the rest of the evening, and then delay eating until mid to late afternoon, or until your usual dinner time.
Simple: Some people enjoy the simplicity of this routine as it’s easy to implement without much planning.
Fasting Mimicking Diet (Prolon)
This diet is carefully calculated to give your body the benefits of fasting and calorie restriction, while still providing a limited amount of food to eat. Day One provides about 1100 calories, while days 2-5 each have 725 calories.
System: Prolon is a week-long, specially designed, packaged meals, reduced calorie fasting diet. Here are some photos of what the product and instructions look like. The program has been designed by USC Professor, Voltar Longo - author of the book, The Longevity Diet.
TIPS AND CONSIDERATIONS
Food
Foods on a fast day: On a modified fast day, choose the foods you do eat wisely. These should be high in protein and fiber. Avoid refined carbs and sugar, which will spike blood sugar and may leave you hungry later in the day.
Fluids: While even water is restricted during the daytime during Ramadan, for purposes of fasting for health, water, or even unsweetened tea or coffee are completely fine to have during a fast. In fact, drinking water is very important, and will make your fasting easier. Be sure to drink enough water and you may feel better by adding some salt to your water. Drinking mineral water may also be helpful.
Succeeding
Goals: Start out with small and realistic goals, knowing that tolerating hunger gets easier over time.
Friends: Fasting is easier with a friend. Find someone to fast with!
Food Environment: Stay out of the kitchen and away from restaurants.
Hunger: It’s okay to be hungry! Hunger-related hormonal signals may actually play very important roles in the beneficial effects of energy restriction on aging and disease susceptibility.
More Tips
Exercise: Do you always need to eat before exercise? The short answer is no, but like most things it really depends on who you are and what your goals are. There are benefits and drawbacks to eating before exercise. Performance can to be better when you have eaten something, but a number of favorable training adaptations can be found by doing both strength and endurance training in the fasted state.
Sleep: If you find that you’re not sleeping as well, or waking up in the middle of the night, reduce the amount of time you’re fasting.
L-Carnitine: 4g/day of this supplement has been shown to make fasting easier. Individuals taking L-Carnitine showed less perceived hunger, less physical fatigue, and reduced fatigue severity vs. individuals not taking the supplement. A caveat is that the trial used intravenous administration not oral dosing (Ref).
DON'T FAST IF YOU…
- Are under high stress (physical or otherwise)
- Are hard-training athletes
- Have liver or other organ diseases
- Are women who is pregnant or trying to conceive
- Are a poor sleeper
- Are underweight
- Are under 18
- Struggle with disordered eating patterns