Is Intermittent Fasting Good for Weight Loss?


The dieting industry is always spinning up new ways to lose weight… and sometimes it brings back old ideas and makes them new again. One dieting approach that has come back into vogue is the idea of fasting (aka not eating), but now there is an additional layer to it… fasting for specific times of the day. This idea has been labeled as “Intermittent Fasting”, a recently popularized strategy for weight loss as well as a theorized way to live longer. 

In this article we are going to discuss intermittent fasting and whether or not it is a good tool for weight loss, and if it is the right tool for you! 

What is Intermittent Fasting?

Intermittent fasting is the name given to a pattern of eating that involves periods of eating and fasting. Essentially, it is a way to restrict your ability to eat to certain times of the day. This approach focuses almost entirely on when you eat and not what you eat. 

The timeframes around the fasting can vary substantially, from a few hours a day to several days at a time, depending on what type of intermittent fasting you decide to follow. 

There are two primary ways that people following the “rules” of intermittent fasting:

  1. They utilize time restricted feeding: this is a pattern that reduces the feeding window in a given day. For example, most people will follow a 16:8 or 20:4 pattern wherein they fast for 16 or 20 hours of the day and can only eat during 8 or 4 hours during the day, respectively. 
  2. They utilize alternate day fasting: this is a pattern of eating where individuals either will eat normally for a day and then take a day off eating or they will eat normally for a day and then eat a very low calorie diet the next day. 

Is Intermittent Fasting Good for Weight Loss?

There have been hundreds of studies conducted on the effectiveness of intermittent fasting for weight loss. Almost all of the studies show that it can be an effective dietary approach/pattern to follow to lose weight. However, all the studies that show effective weight loss also incurred a calorie deficit, which is the mechanism by which intermittent fasting works to drive weight loss. 

By reducing the window of eating (time restricting feeding) or skipping days of eating (alternate day fasting), people consume less calories which leads to weight loss

Is Intermittent Fasting Better Than Other Diets for Weight Loss?

The data suggests that intermittent fasting is not necessarily any better than other approaches for weight loss. For example, one study found that weight loss was similar between a diet that utilizes intermittent fasting and a diet that utilized a “regular” feeding schedule when calorie deficits were equivalent. Another study, a meta-analysis, conducted by a completely separate group found the same thing, and importantly, the results after one year were the same as well. 

What Are The Downsides to Intermittent Fasting?

“There is no free lunch”… this applies to Intermittent Fasting as well. While this approach can lead to weight loss, there are some downsides to consider:

  1. There may be an increased risk of nutrition deficiencies due to the fact that eating windows are shortened and people may decrease the variety of their foods they consume. For example, if you skip breakfast and lunch everyday and you remove major food groups from your diet (like eggs) abruptly, you may miss out on key nutrients like choline. 
  2.  Intermittent fasting may trigger an unhealthy relationship with food in susceptible individuals, leading to obsessive behaviors or an increased risk of developing an eating disorder.
  3. Hunger may become a problem and energy levels may drop if periods of fasting are quite long, such as following an alternate day fasting approach or utilizing a 20:4 time-restricted feeding window. 

Are There Reasons I Should Not Follow Intermittent Fasting?

There are some groups of people that intermittent fasting would be considered “contraindicated for. For example, pregnant women, breastfeeding women, and individuals who are already underweight and/or have a history of disordered eating or nutrient deficiencies should most likely not follow intermittent fasting, especially without supervision of a physician. 

The Wrap Up

Intermittent fasting has become incredibly popular over the last few years as it can be an effective tool for weight loss. However, when examined against other dietary patterns or approaches, it is not any more effective for weight loss. In other words, you can lose weight with this approach but you do not have to fast to lose weight, nor is it more effective than a more balanced approach. 

Consider whether this approach is truly conducive to your goals and if it is something that would be beneficial to you. 

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