When fasting, or intermittent fasting, is mentioned as a topic of discussion, people typically take off running in the opposite direction. For many, fasting does not seem like an attractive option for a healthy lifestyle, but for others, it is a perfect fit.
Traditionally, people fast for religious or health purposes with weight loss as a common byproduct. Although the practice has been around since ancient times, fasting has become an attractive modern day option to support weight management.
Please consult your physician before implementing any new diet, exercise and/or dietary supplement programs, especially if you have preexisting medical conditions or are taking prescribed medications. The statements made on this website are for educational purposes only and are not meant to replace the advice of your physician or healthcare provider.
Intermittent fasting (IF) is a group of individual styles of fasting that involve eating in patterned cycles consisting of periods of fasting and of eating. Simply put, intermittent fasting is the act of fasting for up to 24-36 hours at a time.
The hypothesis behind intermittent fasting is that many individuals consume excess quantities of calories continuously throughout the day that slowly contribute to insulin resistance. In general, continuous production of increased insulin contributes to weight gain over time.
The basic concept of fasting intermittently is that the body goes through cycles of high and low levels of insulin production, which in turn, is thought to help restore insulin sensitivity. Keep in mind that non-insulin resistant individuals may not see weight loss or body composition changes from participating in an IF lifestyle.
It is well established that fasting helps combat effects of aging and aids in promoting cognitive health. The process of autophagy is a cellular “housekeeping” process that breaks down and recycles old proteins and old organelles, microscopic organ-like structures within cells that perform specific functions. Scientists hypothesize that autophagy is the key factor in an “anti-aging” benefit of fasting.
Intermittent Fasting Types
Leangains (aka 16:8 method)
The Leangains or 16:8 Method of intermittent fasting was started by health and fitness expert, Martin Berkhan. The 16:8 method involves fasting for 16 hours and eating during an 8-hour time frame. Most people choose to skip breakfast and eat between 12 – 8 p.m.
- During the 16-hour fasting period, no caloric nutrients are to be consumed. Coffee, tea, zero calorie sweeteners and sugar-free gum are acceptable.
- Interestingly, meal frequency during the eating phase of the fast is not important.
- If your goal is to see an increase in muscle mass and a decrease in fat mass, it is suggested to aim for fasted trainings and eat your largest meal post-workout.
- On rest days, your first meal of the day should be the largest, contrary to workout days, when your largest meal of the day should be consumed post-workout.
- Consume high amounts of healthy protein daily.
- Increase carbohydrate intake on active/workout days only.
As tempting as it may be, it is important not to overeat and make healthy food choices during meal time. Opt for lean protein, fruits and vegetables and refrain from eating refined carbohydrates and fatty foods. Try increasing your protein intake and lower carbohydrate consumption if/when you feel extra hungry during periods of fasting. Remember to consume adequate amounts of liquids throughout the day to maintain proper hydration. The average adult should drink approximately two liters of water (or, one-half of your body weight in ounces) per day.
The Warrior Diet
The Warrior Diet was created by Ori Hofmekler, a well-known nutrition and fitness expert. Hofmekler modeled the Warrior Diet based on the eating patterns of ancient warriors who would eat very little during their active times and then feast during the night in one large meal.
The Warrior Diet intermittent fasting approach involves 20 hours of fasting with four hours of eating. Minimal research exists to support these theories, but it is believed that weight loss is a direct correlation to a reduction in caloric intake. Hofmekler designed a three-week, three-phase plan to support the transition into a Warrior Diet lifestyle:
Week One, Phase I
- Reduce your caloric intake by only consuming raw fruits and vegetables, hard-boiled eggs, broths and vegetables during the other four hours of the day.
- Eat a salad followed by a large meal packed with plant protein such as beans, whole grains and cooked vegetables during the other four hours of the day.
Week Two, Phase II
- Reduce your caloric intake by only consuming raw fruits and vegetables, hard-boiled eggs, broths and vegetable juice for 20 hours during the day.
- Eat a salad followed by a large meal packed with lean animal protein, cooked vegetables and a handful of nuts during the other four hours of the day.
- No grains or starchy foods should be eaten during Phase II.
Week Three, Phase III
- Alternate between high carbohydrates for two days and high protein and low carbohydrates for two days.
- During the high carbohydrate days you will follow the same eating pattern as in Phase I.
- On the high protein, low-carbohydrate days, follow the same eating pattern as in Phase I, but replace plant protein with animal protein and add one side of vegetables that is low in complex carbohydrates (i.e. starch).
Created by Dr. Michael Mosley, the 5:2 Diet and intermittent fasting approach involves eating normally for five days a week and restricting calories to approximately 500 calories for the remaining two days of the week. It is important to note that the two fasting days are not intended to be back-to-back. A popular fasting cycle is to space out your fasting days. For example:
If you are incorporating exercise, Mosley suggests making your rest days coincide with your low-calorie days. According to Dr. Mosley, the best practice is to reduce the amount of refined carbohydrates and increase the amount of healthy protein you consume. On non-fasting days, try not to overeat or binge. The rationale behind the success of the 5:2 diet is the incorporation of restricted feeding times and calorie reduction.
Intermittent Fasting Cautions:
- If you are pregnant or trying to become pregnant, do not try intermittent fasting.
- People with Type I diabetes should not try IF.
- If not careful, IF can create or exacerbate eating disorders.
- IF may create an unhealthy relationship with food. If you notice that you become overly obsessed with food or start to binge during your meal times, stop fasting and seek the help of a medical professional.
Intermittent Fasting Benefits:
- Intermittent fasting improves body composition with decreased fat mass.
- Supports healthy aging.
- Research shows that fasting may improve biomarkers for disease, reduce oxidative stress and preserve learning and memory functioning.
- Consult with your physician to determine if intermittent fasting is right for you.
- Drink lots of water. Many people mistake thirst for hunger.
- During fasting that requires no food consumption, be mindful not to drink anything that contains calories. If you need coffee, drink coffee with non-caloric sweeteners and no dairy (some drinks and chewing gums may be sugar-free but not calorie free).
- When eating, try not to overindulge.
- Choose an intermittent fasting technique that is sustainable for you. The goal of IF is to see healthful results.
- Be thoughtful about your meals. Try meal prepping to reduce the likelihood of overeating or making poor food choices after fasting.
Intermittent Fasting has been around for a very long time; although it may work for some, it may not work for all. The key takeaway here is that it’s important to seek out an eating program that works best for you and your individual healthy lifestyle goals. This could mean eating four to six small meals throughout the day, three large meals or restricting your food intake to specific times each day in the form of IF. And, remember – it is critically important to consult with your physician before starting any new eating regimen.
If you decide to try intermittent fasting, which method do you think might work best for you?
Longo, Valter D., and Mark P. Mattson. “Fasting: Molecular Mechanisms and Clinical Applications.” Cell metabolism 19.2 (2014): 181–192.
Mindikoglu, Ayse L. et al. “Impact of Time-Restricted Feeding and Dawn-to-Sunset Fasting on Circadian Rhythm, Obesity, Metabolic Syndrome, and Nonalcoholic Fatty Liver Disease.” Gastroenterology Research and Practice2017 (2017): 3932491.
Gabel, Kelsey et al. “Effects of 8-Hour Time Restricted Feeding on Body Weight and Metabolic Disease Risk Factors in Obese Adults: A Pilot Study.” Nutrition and Healthy Aging 4.4 (2018): 345–353.
Collier, Roger. “Intermittent Fasting: The Science of Going without.” CMAJ : Canadian Medical Association Journal 185.9 (2013): E363–E364.
Moro, Tatiana et al. “Effects of Eight Weeks of Time-Restricted Feeding (16/8) on Basal Metabolism, Maximal Strength, Body Composition, Inflammation, and Cardiovascular Risk Factors in Resistance-Trained Males.” Journal of Translational Medicine 14 (2016): 290.