Last week’s blog explored ketogenic diets. This week, I’m exploring another diet that seems to be all the rage. The topic of the week: intermittent fasting.

As the name suggests, intermittent fasting involves not eating or drastically reducing food intake for time periods lasting anywhere from 16 hours to up two days in length. There are many different protocols for intermittent fasting. Some of the more popular protocols for intermittent fasting include:

  • Eat normally for five days followed by two fast days in which 500-600 calories per day are consumed.
  • 500-600 calories every other day with normal eating in between these fasting days.
  • Fast for 16 hours of the day and eat only during an 8-hour period of a day. For instance, some people will skip breakfast and won’t eat anything after 8 pm.

Research on intermittent fasting has shown numerous positive benefits, such as reduced inflammation, improved asthma symptoms, reduced blood pressure and cholesterol, and improved insulin sensitivity to name a few. Most of these benefits can be attributed to the weight loss associated with intermittent fasting. Weight loss is the primary reason that people follow an intermittent fasting diet and can be contributed to the ketosis that is stimulated during the fasting period. For more on ketosis, check last week’s blog: here.

Despite the research showing the above benefits, there really is not much long-term research on the effects of intermittent fasting. What also makes me a little bit skeptical about the research is that there are so many different protocols for intermittent fasting. As a result, it is not very standardized.

It should be noted that during non-fasting days, overeating or bingeing is not allowed. It’s certainly not a free for all during this time. Rather a “normal” eating day is supposed to be followed. This can be hard for some people since they may feel over hungry due to the preceding fast. Intermittent fasting is also not appropriate for many people, such as those who are pregnant, diabetic or on medication. It’s also not recommended for those with a history of an eating disorder or disordered eating since the fasting can be a potential trigger. I would also say that intermittent fasting is not suitable for athletes, since exercise shouldn’t be done on the fasting days and the fasting can interfere with proper recovery.

Other cons of intermittent fasting include its interference with social life. Most social activities are centered around food and most people have a hard time being around food when they’re not allowed to eat. Additionally, most people have extremely low energy during the fasting period, which interferes with both physical activity and productivity. Think about the negative impact that this could have on your family and loved ones not only because of the negative example you’ll be setting by not eating, but also because you’ll most likely be tired, cranky and unable to fully engage during the fasting period.

Intermittent fasting is not a dead set way of losing weight. You can’t overeat during the non-fast period and still expect to lose weight. Intermittent fasting could even cause weight gain for some people because of its impact on metabolism. A fast as short as even 24 hours has been shown to reduce resting metabolic rate. During the fast, the body may go into a “starvation” mode. As a result, when food is consumed again after the fasting period, it may result in weight gain because of the lowered metabolism.

Despite the short-term research, there is simply not enough long-term research to support or recommend intermittent fasting. I also believe all the potential cons associated with this diet far exceed the potential benefits. As seems to be the trend with my recent blogs, it’s just another “fad” diet. I may sound like a broken record, but the best diet is one that you don’t know you’re on. I think it’s most important to choose something that is sustainable and will keep weight off long-term, rather than result in a cycle of yo-yo dieting.