Intermittent Fasting Diet Guide: Analyzing The Cycles Of Feast And Famine

Our nutrition coach shares the how to and benefits of time-restricted eating

As a UESCA-certified endurance nutrition coach and a NASM-certified nutrition coach, I work with a lot of endurance and strength athletes who want to get fitter and stronger but also leaner and healthier. 

For this reason, many everyday athletes are looking for the best weight loss diets.

The practice of fasting for weight loss and health has been around for thousands of years, but intermittent fasting diets have become massively popular in recent years.

But, what are the different types of intermittent fasting? How do you follow an intermittent fasting diet?

In this intermittent fasting diet guide, we will discuss what intermittent fasting entails, the types of intermittent fasting diets, and how to follow them for weight loss.

Let’s get started! 

A clock on an empty plate.

What Is Intermittent Fasting?

Intermittent fasting refers to a dietary approach that involves deliberately abstaining from consuming food and caloric beverages for an extended and predetermined period of time. 

Benefits of intermittent fasting diets can include:

Everyone experiences at least several hours of fasting every day, termed the overnight fast, which occurs during sleep.

There are contraindications to some of the different types of intermittent fasting diets, particularly in cases of extended fasts such as a 24 hour fast or alternated-day dating.

Intermittent fasting diets for those who are pregnant or breastfeeding, have a history of an eating disorder, are underweight according to BMI, have diabetes or another metabolic condition, take certain medications, or have other chronic health conditions may have negative effects.

This is why it is important to speak with your doctor before trying some of the different types of intermittent fasting diets that involve prolonged periods of fasting. 

Moreover, if you are trying to find the best type of intermittent fasting for weight loss, again, you should consult your doctor or work with a registered dietitian nutritionist to decide if one of the different types of intermittent fasting is best for you or if a more effective approach to weight loss would be a balanced, calorie-controlled diet with exercise.

A clock, plate and the words intermittent fasting on a notebook page.

What Are the Different Types of Intermittent Fasting Diets?

Intermittent fasting is one of the most popular types of fasting for weight loss and health.7Rynders, C. A., Thomas, E. A., Zaman, A., Pan, Z., Catenacci, V. A., & Melanson, E. L. (2019). Effectiveness of Intermittent Fasting and Time-Restricted Feeding Compared to Continuous Energy Restriction for Weight Loss. Nutrients11(10), 2442. https://doi.org/10.3390/nu11102442

Rather than being a specific type of weight loss diet, intermittent fasting is a broad category of a type of dieting approach such that there are all sorts of iterations and variations on intermittent fasting diet patterns.

This means that there isn’t one specific intermittent fasting diet or intermittent fasting diet schedule, but rather many different ways that you can follow an intermittent diet for weight loss or health.

The two primary categories of intermittent fasting diets are time-restricted intermittent fasting diets and alternate-day intermittent fasting diets.

A clock wit the words eat and fast on it.

Time-Restricted Intermittent Fasting Diets

All types of intermittent fasting diets involve dividing up the 24-hour day into a fasting window and eating window with some sort of deliberate pattern that involves extending the period of overnight fasting and then limiting the window of time that you can consume caloric foods and beverages each day.

There are many different intermittent fasting schedules that use the time-restricted fasting approach.

With any of these time-restricted intermittent fasting diet plans, you have complete flexibility in terms of how you schedule your fasting and eating windows.

For example, with the 18/6 intermittent fasting diet, you have an 18-hour fast and a 6-hour eating window per day.

Thus, you might use 12 AM to 6 PM, 11 AM to 5 PM, or 2 PM to 8 PM for your eating window and then have an 18-hour fast the rest of the day and night.

However, it is entirely up to you and certainly doesn’t have to be done right on the hour, as long as you are sticking with the 18-hour fast and 6-hour eating blocks of time.

A clock split up in 16 and 8 hours with utensils.

Intermittent fasting diets with shorter fasts are easier logistically and more similar to how people normally schedule their food intake8Gill, S., & Panda, S. (2015). A Smartphone App Reveals Erratic Diurnal Eating Patterns in Humans that Can Be Modulated for Health Benefits. Cell Metabolism22(5), 789–798. https://doi.org/10.1016/j.cmet.2015.09.005 but may not offer all of the potential benefits of fasting for longer durations.9Kerndt, P. R., Naughton, J. L., Driscoll, C. E., & Loxterkamp, D. A. (1982). Fasting: the history, pathophysiology and complications. The Western Journal of Medicine137(5), 379–399. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1274154/

‌For example, autophagy and significant increases in growth hormone can take close to 48 hours to really take effect.

Even getting into ketosis generally takes 18-24 hours, depending on factors such as your body size, your diet composition, if you are an endurance-trained athlete, and if you have been performing exercise while fasting.10Weltan, S. M., Bosch, A. N., Dennis, S. C., & Noakes, T. D. (1998). Influence of muscle glycogen content on metabolic regulation. American Journal of Physiology-Endocrinology and Metabolism274(1), E72–E82. https://doi.org/10.1152/ajpendo.1998.274.1.e72

Some of the common time-restricted intermittent fasting diet schedules include the following:

A clock and a salad.

Alternate-Day Fasting

Alternate-day fasting, also called ADF fasting for short, is an approach to intermittent fasting diets that uses a fasting schedule for the week as a whole scale rather than each individual day.

This type of intermittent fasting diet involves fasting every other day and then consuming what you want to eat, and when you want to eat it on the days you are not fasting.

With strict alternate-day fasting diets, you do a full 24-hour water fast every other day and eat normally at liberty on alternate days. 

There are also modified alternate-day intermittent fasting diets such as the 5:2 diet, also known as the Fast Diet, the 5&2 diet, or the 5/2 diet.

This type of intermittent fasting diet is so named because it involves following your regular diet and caloric intake for five days of the week and then severely restricting calories (to 500–600 per day) the other two days of the week.

OMAD

OMAD is a type of fasting that entails eating only one meal a day.

This is essentially a 23-hour fast.

A person eating a salad.

How Do You Do Intermittent Fasting?

Unlike most weight loss diets and even lifestyle diets geared towards overall health, the intermittent fasting diet approach does not dictate what you can and cannot eat.

Rather, intermittent fasting diets are defined as restricting when you can and cannot eat.

Therefore, there aren’t any rules about the foods to eat on an intermittent fasting diet, and there aren’t any intermittent fasting diet meal plans that you necessarily have to follow.

You can even combine intermittent fasting with another type of diet that does involve putting guidelines on the types of foods that you can and cannot eat or the macro ratios (carbohydrates, fats, and proteins) to consume.

For example, you might follow the 16/8 intermittent fasting diet and the vegan diet simultaneously, meaning that you will fast 16 hours every day and eat for only eight hours. 

During those eating hours, you will be eating only plant-based foods, eliminating all meat, poultry, seafood, fish, eggs, dairy, and animal byproducts from your diet.

Of course, if you are trying to follow an intermittent fasting diet for weight loss, you will still need to be mindful of your caloric intake because a caloric deficit is needed to lose weight whether or not you are intermittent fasting or eating at regular intervals or at liberty.

A person eating a salad.

That said, intermittent fasting for weight loss is a potentially successful approach for some people. By restricting the window in which you can consume calories, you are putting a hard start and hard stop on caloric consumption.

This can reduce mindless eating at night and can force you to be more deliberate in your food choices.

More practically, the fewer hours you have to eat in a day, the fewer calories you will likely be able to consume unless you have a massive binge during your intermittent fasting eating window.

Overall, an intermittent fasting diet can be a successful way to lose weight, manage a healthy weight, and support various health goals. 

It is highly recommended that you speak with your healthcare provider before beginning any of these types of fasting, particularly more aggressive intermittent fasting diets or prolonged fasting.

If you are intrigued by the potential benefits of fasting, you can read more about them here.

A person smiling while eating a waffle.

References

  • 1
    Tinsley, G. M., & La Bounty, P. M. (2015). Effects of intermittent fasting on body composition and clinical health markers in humans. Nutrition Reviews73(10), 661–674. https://doi.org/10.1093/nutrit/nuv041
  • 2
    Johnson, J. B., Summer, W., Cutler, R. G., Martin, B., Hyun, D.-H., Dixit, V. D., Pearson, M., Nassar, M., Tellejohan, R., Maudsley, S., Carlson, O., John, S., Laub, D. R., & Mattson, M. P. (2007). Alternate day calorie restriction improves clinical findings and reduces markers of oxidative stress and inflammation in overweight adults with moderate asthma. Free Radical Biology and Medicine42(5), 665–674. https://doi.org/10.1016/j.freeradbiomed.2006.12.005
  • 3
    Bhutani, S., Klempel, M. C., Berger, R. A., & Varady, K. A. (2010). Improvements in Coronary Heart Disease Risk Indicators by Alternate-Day Fasting Involve Adipose Tissue Modulations. Obesity18(11), 2152–2159. https://doi.org/10.1038/oby.2010.54
  • 4
    Bagherniya, M., Butler, A. E., Barreto, G. E., & Sahebkar, A. (2018). The effect of fasting or calorie restriction on autophagy induction: A review of the literature. Ageing Research Reviews47, 183–197. https://doi.org/10.1016/j.arr.2018.08.004
  • 5
    Home Page: The American Journal of Clinical Nutrition. (n.d.). Ajcn.nutrition.org. https://ajcn.nutrition.org/
  • 6
    Barnosky, A. R., Hoddy, K. K., Unterman, T. G., & Varady, K. A. (2014). Intermittent fasting vs daily calorie restriction for type 2 diabetes prevention: a review of human findings. Translational Research164(4), 302–311. https://doi.org/10.1016/j.trsl.2014.05.013
  • 7
    Rynders, C. A., Thomas, E. A., Zaman, A., Pan, Z., Catenacci, V. A., & Melanson, E. L. (2019). Effectiveness of Intermittent Fasting and Time-Restricted Feeding Compared to Continuous Energy Restriction for Weight Loss. Nutrients11(10), 2442. https://doi.org/10.3390/nu11102442
  • 8
    Gill, S., & Panda, S. (2015). A Smartphone App Reveals Erratic Diurnal Eating Patterns in Humans that Can Be Modulated for Health Benefits. Cell Metabolism22(5), 789–798. https://doi.org/10.1016/j.cmet.2015.09.005
  • 9
    Kerndt, P. R., Naughton, J. L., Driscoll, C. E., & Loxterkamp, D. A. (1982). Fasting: the history, pathophysiology and complications. The Western Journal of Medicine137(5), 379–399. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1274154/
  • 10
    Weltan, S. M., Bosch, A. N., Dennis, S. C., & Noakes, T. D. (1998). Influence of muscle glycogen content on metabolic regulation. American Journal of Physiology-Endocrinology and Metabolism274(1), E72–E82. https://doi.org/10.1152/ajpendo.1998.274.1.e72
Photo of author
Amber Sayer is a Fitness, Nutrition, and Wellness Writer and Editor, as well as a NASM-Certified Nutrition Coach and UESCA-certified running, endurance nutrition, and triathlon coach. She holds two Masters Degrees—one in Exercise Science and one in Prosthetics and Orthotics. As a Certified Personal Trainer and running coach for 12 years, Amber enjoys staying active and helping others do so as well. In her free time, she likes running, cycling, cooking, and tackling any type of puzzle.

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