By Casey Seamon, Registered Dietitian

The world of weight loss can be an overwhelming and confusing place. It seems like every day a new super supplement or quick fix fad diet is popping up promising to help you shed unwanted weight rapidly.

While the ideal approach to weight loss is to aim for 1-2 pounds a week using a well-balanced diet and regular exercise, the temptation to subscribe to the next popular craze can be too much to ignore.

So, each month, we’re examining a different diet—diving into the science behind it, the pros, the cons—and letting you decide whether or not it’s worth trying.

Intermittent Fasting

This month we’re going to take a closer look at Intermittent Fasting. The practice of fasting has been around for ages and has taken on many different shapes and forms over the years. Some people have used fasting for political or religious reasons, and others have just accidentally fasted because they were too busy to make breakfast!

The main idea of fasting is to abstain from eating for significant periods of time. While there are numerous ways to complete a fast, the three main variations of Intermittent Fasting are whole day, alternate-day and time-restricted fasting.

  • In whole-day fasting, you eat normally on five to six days of the week and restrict intake to no more than 500 calories for the remaining one or two days.
  • Alternate day fasting is just as it sounds: you fast every other day, which can mean no food at all, or, again, limiting your intake to 500 calories.
  • Finally, time-restricted fasting allows you to eat whatever you want for a four-eight hour window and completely restrict your intake to water for the remaining 16-20 hours of the day. No matter which variation strikes your fancy, the science remains the same.

The Science

When you break it down, the science behind weight loss is actually quite simple. If you eat more calories than you burn off, you will gain weight. If you eat fewer calories than you burn off, then you will lose weight. And if you eat the same amount of calories that you burn off, you will maintain your current weight.

Intermittent fasting works to help you lose weight by restricting caloric intake and therefore putting your body in a calorie deficit. When your body doesn’t have its primary fuel source (carbohydrates) readily available from dietary intake, it looks to your fat stores for energy. Brief fasts of 16-24 hours force your body to access that fat for fuel and thus help you shed pounds.

The Pros

Here are the top three benefits to trying Intermittent Fasting:

  1. The biggest benefit to this diet is that it gets you thinking about when and what you are eating. Paying attention to your diet is bound to help you achieve goals.
  2. Some research shows that fasting may improve insulin sensitivity, as well as reduce inflammation in the body.
  3. If done correctly and safely, Intermittent Fasting can also help you lose unwanted fat, which has obvious health benefits.

The Cons

Here are three potential downsides to consider with Intermittent Fasting:

  1. There is little guidance as to what you should be eating when you’re not fasting. If you are binging on high-calorie, unhealthy foods, then it’s not likely you’ll lose any weight. The nutrient content of the food you eat is highly important, and without much direction, it’s very easy to overdo it at mealtimes.
  2. Those with issues regulating blood sugar or taking insulin injections could suffer from severe hypoglycemic episodes, so it is not advised that they abide to strict fasting periods. 
  3. There’s a pretty high dropout rate with this diet because many people find it hard to go significant periods of time without eating. You may be better off with overall calorie restriction on a daily basis, which can help you meet the same goal of losing weight.


Hopefully this breakdown helps you understand some of the ins and outs of this popular diet. Ultimately, it’s up to you to decide which approach to nutrition is right for you. Consulting with your doctor and/or a registered dietitian can also help you find the healthiest, safest ways to lose weight and eat better. Check back next month when we break down Whole 30 and see what it’s all about.

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