Fad Diets Debunked: The Intermittent Fasting Diet

Intermittent Fasting

After all the fun I had coming up with my detox diet post, I thought I would make a series of it and review a few of the most popular diet trends out there! Today, I wanted to chat about the intermittent or alternate day fasting diet. Have you heard of this one? A few wildly popular books have been published recently toting this diet by different names like: The 5:2  Diet, The Fast Diet, or The Overnight DietI know women’s health magazines and various blogs have been talking about this diet a lot over the past few months. However, is it really worth all the hype? Here’s the basic concept of the diet:

  • Eat your normal diet (or a little bit healthier version of your normal) 4-6 days of the week
  • On the off days you will either completely fast for close to 24 hours or drastically restrict your calories to about 25% of your needs. Another way to achieve the fast period is by skipping two meals one day.
  • Weight loss occurs because during your fast days, your body goes through your stored energy (glycogen) and then begins to use fat as an energy source

So, to lose weight all you have to do is fast a couple of days a week – no changes in your non-fast day diet required? Hmm… let’s take a closer look at the published research behind this diet concept and see what you think. To date, most of the research has been on mice so it is difficult to relate those same benefits to humans. Also, almost all human studies have been conducted at the same medical facility – University of Illinois in Chicago. Most have lasted on a few weeks, so we still have no data on long-term effects of this type of diet.

  • 16 obese adults followed an alternate day fasting diet (eat one day, “fast” on 25% energy needs the next) for 8 weeks and lost an average of 5.8% of their original body weight. They also noted a significant decrease in total cholesterol, LDL cholesterol, and triglycerides. (Source)
  • A group of 8 non-obese men and 8 non-obese women fasted every other day for 22 days and lost an average of 2.5% of their body weight. Of note, hunger did not decrease on fast days over time so many subjects felt the diet wasn’t sustainable in the long-term. (Source)
  • No significant or consistent positive effects on blood sugar have been found using alternative day fasting to date. (Source)
  • The effect of intermittent fasting on cancer risk is yet to be tested in humans, but mice studies show it might be protective against certain types of cancer. (Source)

My take home message for those thinking about intermittent/alternative day fasting? It may be a great idea in theory, but I feel like making simple, healthy diet changes will be a lot more effective for weight loss in the long run. Plus, the research out there on the subject is still very limited. You may see a pound or two come off in the first couple of weeks you try intermittent fasting, but over time, you will get much better results by changing the type of food you eat, not the timing.

What do you think? Have you ever tried intermittent fasting? 


2 thoughts on “Fad Diets Debunked: The Intermittent Fasting Diet

  1. You are making a good point, arguing with science. I think I can agree with you on one thing: Intermittent fasting alone doesn’t solve problems. It may work if it’s combined with a good diet.

    I personally believe that intermittent fasting is effective if combined with a low carb or no carb diet. A permanently moderate blood sugar level, no insulin overkill, keeping carbs away from people… al these things in combination for several hours a day would really force the body to burn fat.

    The only downside to this theory: Because scientists only focus on one aspect at a time, they don’t try a study of intermittent fasting AND a real low carb diet. That would be the trick.

    Anyway, thanks for being diplomatic about your judgement on intermittent fasting.

    • Thanks so much for sharing your thoughts, Michael! Although I’m not convinced from my research that intermittent fasting is the miracle weight loss solution some believe, I would love to see what would happen if combined with a whole foods or low carb diet. There have been a few new studies showing that low carb diets may be an effective option for people looking to lose weight (it was for my boyfriend!). Definitely something it would be interesting to explore!

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