An Overview of Intermittent Fasting Diets

Featured in the Bastyr University Clinic Blog

From Hugh Jackman to JLo, intermittent fasting seems to be the way to earn that incredible body glamorized on screen.  Although dieting may not get you nominated for a Grammy or give you Wolverine-like super powers, let’s take a look at what can be gained from intermittent fasting!


By definition, fasting means the complete avoidance of food.  Intermittent fasting means that you still eat, but maybe at a later time than you normally would.

There are many different ways to fast.  Intermittent fasting programs have calorie limits, but these limits may not necessarily be required.  For example, many modified intermittent fasting programs allow one meal during a “fasting day” that makes up 25% of your calorie needs.

Intermittent fasting diets fall into three groups.  One group is alternate-day fasting.  This diet has you alternate between days you can eat what you want and days you are supposed to fast.  Second, there is whole day fasting.   During whole day fasting you fast 1 to 2 days per week.  On the other days you can eat anything anytime.  Lastly, there is time restricted eatingTime restricted eating involves a routine where you only have a certain number of hours to fast and a certain number of hours to eat daily.



Intermittent fasting may be an effective way to reduce daily calorie intake.  Other potential benefits include weight loss, lower body fat, lower total cholesterol and resistance to age-related diseases.  Other studies have shown that intermittent fasting may be just as effective as watching what you eat and reducing your daily calories.

Researchers have discovered that one reason short-term intermittent fasting may work is because your body increases its reliance on fat for energy.  This has be the case especially within the first 24 hours of fasting and to peak between 18 and 24 hours of fasting.  Also, it has been shown to increase resting metabolic rate (a.k.a. BMR, basal metabolic rate).


There are a few things to think about when looking into applying intermittent fasting to help you
lose weight.  Researchers are discovering that very-low calorie diets don’t have better long-term weight loss results than less extreme diets.  However, if you find it difficult to monitor your calories in the first place, intermittent fasting may be a reasonable way to restrict calories for weight loss.   This is especially the case since most people tend to reduce the amount they eat when they only have 1 meal per day.  During that one meal, they tend to feel fuller sooner.

Although some intermittent fasting diets may be more difficult – having you fast for 20 hours and only allowing time to eat for 4 hours – there are other versions that may be easier to follow.  For Jennifer Thinkingexample, a 16 hour fast followed by an 8 hour eating window is very similar to those of us that regularly skip breakfast and dinner.

Practicing a diet that encourages starvation does pose the following risks:

  • Possible increase in fat above initial levels, especially upon weight regain after the weight loss
  • Vitamin and mineral deficiencies
  • Falling short of the general nutrition guidelines for carbohydrates, proteins and fats
  • Muscle loss

There hasn’t been adequate research done on time-restricted eating to compare it to regular dieting, nor do scientist know enough about the effects of intermittent fasting on exercise performance.  If you decide to incorporate intermittent fasting into your lifestyle, please consult your doctor!


Tinsley, G. M., & La Bounty, P. M. (2015). Effects of intermittent fasting on body composition and clinical health markers in humans. Nutrition Reviews, 73(10), 661–74.


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