Intermittent Fasting Pros and Cons

Advantages and Disadvantages Explained by Bodybuilding Nutritionist

By: Jeremy Fox, CNC, CPTUpdated: March 20, 2024

If you’re reading this, you may be unsure whether to try intermittent fasting. Most importantly, you may want to know if it actually helps with weight loss or is just another passing diet trend.

You have come to the right place. I am a certified nutrition coach and will provide an unbiased evaluation of intermittent fasting’s advantages and disadvantages so you can decide if it’s the right option for you.

intermittent fasting pros and cons

What Is Intermittent Fasting?

Intermittent fasting is a time-restricted eating pattern involving alternating fasting and eating periods. The idea is that the fasted state burns body fat stores for energy, helping you lose more weight.

However, the main reasons for the potential benefits have more to do with reduced food intake, which creates a calorie deficit.

The most common form of intermittent fasting involves restricting your daily eating window to a specific period, usually between 6 and 8 hours, and fasting for the remaining hours.

Other types of intermittent fasting involve restricting calories for a longer period of time, such as a full day or multiple days per week.

Types of Intermittent Fasting

  • Time-Restricted Feeding: This method involves daily fasting followed by designated periods of eating. The most common schedule involves a 16-hour fasting period and an 8-hour eating window, also called 16:8 intermittent fasting. However, the amount of time can be adjusted.
  • Alternate-Day Fasting: This type of intermittent fasting involves alternating between days of unrestricted eating and days of significant calorie restriction. On the fasting days, most people consume only 500-600 calories. 
  • 5:2 Fasting: This diet involves eating normally five days a week and restricting calorie intake to 500-600 calories on the remaining two days.
  • Fasting Mimicking: This type of intermittent fasting involves eating a low-calorie, plant-based diet for five consecutive days once every few months.

Here’s what I learned from 5 days on the fasting-mimicking diet.

Intermittent Fasting Notepad and Clock

Pros and Cons of Intermittent Fasting

In this section, I’ll outline some of intermittent fasting’s beneficial effects and potential drawbacks. I’ll provide seven benefits of intermittent fasting and seven downsides for a balanced assessment.

Pros of Intermittent Fasting

  1. Provides Structure: Intermittent fasting’s framework is easy to grasp. Basic instructions like “only eat between noon and 8 pm” provide specific instructions encouraging people to act.
  2. Increases Insulin Sensitivity: Fasting is the simplest way to lower blood sugar levels, which in turn lowers insulin levels. Intermittent fasting also reduces insulin resistance1, making your body more efficient at utilizing carbs when you eat. 
  3. Heart Health Benefits: Studies show intermittent fasting diets have a positive effect on lipid metabolism, such as improving total cholesterol, LDL cholesterol, and triglyceride levels2.  
  4. No Tracking Required: Intermittent fasting generally doesn’t require calorie counting or tracking macros like traditional diets. Instead, most IF diets permit eating as much as you want during the eating window. 
  5. Easier Meal Prep: Most people consume fewer meals while intermittent fasting due to the shorter time frame in which you can eat. This means you typically don’t have to cook or prepare as many meals, which can be a significant plus for busy people.
  6. Feel Full More Often: A typical calorie-restricted diet eventually causes you to feel hungry much of the time. With intermittent fasting, you will usually feel full during your eating window.
  7. Allows Flexibility: Unlike popular diets such as keto or paleo, you are not required to eliminate any food groups or specific types of food with intermittent fasting.

When I fast for part of the day, I often feel more mental clarity than I do after eating. I also like intermittent fasting because it frees up time for more work or relaxation during the fasting period.

On IF diets, I enjoy feeling full for a portion of the day. That’s something I wasn’t used to during bodybuilding contest prep.

Cons of Intermittent Fasting

  1. Can Cause Overeating or Undereating: Intermittent fasting is based on the premise that you will eat fewer calories due to the restricted time frame. However, the increased hunger caused by fasting can result in eating more than you normally would, leading to weight gain. Conversely, too short of an eating window can cause people to undereat, which has negative metabolic consequences.
  2. Can Be Difficult At First: If you’re not used to going more than a few hours without eating, fasting for most of the day may be challenging. The most common complaints are hunger, irritability, and headaches.
  3. Side Effects: Low blood sugar while intermittent fasting can cause more severe issues, such as weakness, light-headedness, or nausea. You may need to contact a physician if you experience these symptoms.
  4. Requires Some Discipline: Intermittent fasting requires enough self-control to go without food for several hours, even when hungry. While this can be a major problem for some people, it’s also an opportunity to build mental fortitude. 
  5. Awkward Social Situations: People will likely ask why you’re not eating during your fasting window. Fasting at events with family or friends sometimes leads to uncomfortable peer pressure to socialize with food.
  6. Encourages Binge Eating: Intermittent fasting can result in uncontrolled eating or eating excessive amounts of food in a short time. This can be a slippery slope, especially if you have an eating disorder.
  7. Not for Everyone: Intermittent fasting can also be potentially dangerous for people with health conditions such as hypoglycemia, diabetes, or acid reflux.

The first time I tried intermittent fasting, I felt weak in the knees for the first couple of days. But my body quickly adapted to where I could fast for a full day pretty easily.

However, I found intermittent fasting more challenging to stick with after prolonged periods of calorie restriction, such as weeks or months of cutting weight.

intermittent fasting pros and cons

Does Intermittent Fasting Work?

A systematic review of studies suggests moderately high-quality evidence supporting intermittent fasting for weight loss and reducing the risk of heart disease3. However, new research indicates intermittent fasting is comparable to continuous calorie restriction for weight loss4.

This means that intermittent fasting is not magic, and it’s definitely not a get-out-of-jail-free card that allows you to eat whatever you want. Instead, it’s mostly a strategy to reduce caloric intake.

As a nutrition coach, I recommend starting with a balanced diet and an appropriate calorie deficit to lose weight. Once you’ve dialed in the major factors, you can start playing with nutrient timing and eating windows to see if they enhance your results.

In my experience, intermittent fasting can be an effective strategy when paired with proper energy balance and healthy eating. It also has some potential benefits for improving insulin function, especially for overweight and obese people.

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Intermittent Fasting FAQ

For those considering implementing an intermittent fasting regimen, you probably have more questions. So here are my short answers to some of the most common queries.

How Long Should You Fast?

The most popular fasting routine is 16 hours of fasting and 8 hours of eating. But you can reduce the fasting window to 14 hours if you find it hard to eat enough. Or you can extend it to 18 hours for maximum fasting benefits.

There is no right or wrong fasting duration, so pick one that works best with your schedule and fitness goals.

What Does Intermittent Fasting Do?

Intermittent fasting generally helps people eat less, which can help with weight management. The periods of fasting may also have additional health benefits such as lowering fasting glucose levels and increasing insulin sensitivity.

What to Eat During Intermittent Fasting?

While some people eat nothing during the fasting period, others prefer to eat small, low-carb meals that help maintain low insulin levels. Examples of such meals include vegetables, oils, nuts, and seeds.

During the eating window, it’s essential to consume healthy, whole foods that will provide your body with the necessary nutrients to get the most out of intermittent fasting.

What Can You Drink During Intermittent Fasting?

It is permissible to consume low-carb beverages during fasting. However, it is recommended that you avoid drinking milk, juice, or soda, as they are high in calories.

Water is the best drink during fasting, as it keeps you hydrated and helps curb hunger. Additionally, low-calorie beverages such as tea and coffee can also be consumed.

Can You Drink Coffee While Intermittent Fasting?

Yes, you can drink black coffee while intermittent fasting since it has no sugar and almost no calories. But it should go without saying that you can’t drink that Double Chocolaty Chip Frappuccino from Starbucks!

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By |March 20, 2024|Nutrition|0 Comments
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