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Intermittent fasting pros and cons

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Posted on July 16, 2021

Intermittent fasting pros and cons

According to Google Trends, intermittent fasting was 2020's second most searched diet (falling from the top spot in 2019). While the intermittent fasting diet trend seems to be here to stay, questions remain about it's effectiveness, longevity and who is best suited for this type of restrictive dieting. St. Vincent Charity Medical Center registered dietitian Staci Cortelezzi discusses facts and misconceptions of intermittent fasting and weighs in on if it's a long-term solution of weight loss


Three types of intermittent fasting have gained the most popularity:

  1. Time-restricted fasting. With style of intermittent fasting, dieters set fasting and eating windows for each day. For example, one might fast for 16 hours of the day, only eating during the remaining eight hours. Studies indicate that time-redistricted fasting may be the most viable long-term option. One study showed that after other types of intermittent fasting most of the test subjects went back to their old way, whereas, after the time-restricted type, the majority of subjects were interested in continuing.
  2. Another favored approach is alternate-day or 5:2 intermittent fasting method. With this fasting diet, female fasters eat 500 calories and male fasters eat 600 calories two days a week. During the other five days, fasters maintain a normal diet. However, experts warn this more restrictive fasting can promote unhealthy relationships with food or maybe unhealthy eating habits. The 5:2 method may also promote overeating on non-fasting days.
  3. Whole-day fasting or Eat Stop Eat is the most extreme form of intermittent fasting. Eat Stop Eat involves a 24-hour fast once or twice per week. Fasting from dinner one day to dinner the next day amounts to a full 24-hour fast. Only water, coffee, and other zero-calorie beverages are allowed during the fast, but no solid foods are permitted. If this is being done to manage weight, it’s very important to stick to your regular diet during the eating periods. Fasters should eat the same amount of food as if they hadn’t been fasting at all. The potential downside of this method is that a full 24-hour fast may be fairly difficult for many people.


Asked who should refrain from fasting, Staci Cortelezzi, registered dietitian-nutritionist at St. Vincent Charity Medical Center, says those with a history of eating disorders should steer clear.

“Just because it’s more of a restrictive approach,” Cortelezzi says. Additionally, it may not be suitable for those who are pregnant or breastfeeding.

“You need to make sure you have enough nutrition – your needs are higher during those times,” Cortelezzi adds. “And then definitely if you have any kind of health condition or you’re taking medications, you want to talk to your doctor first, especially if your medications correlate with your food.”

For diabetics who are on insulin, fasting can “really mess with their medication” and potentially cause low blood sugar, she says. When selecting an intermittent fasting method, Cortelezzi says the No. 1 thing to consider is sustainability.

“If you’re not able to keep up with it or sustain it for a long term,” Cortelezzi says, “it’s likely not going to yield the long-term results, or you might lose some weight initially then when you go off of it, you’ll likely gain the weight back.”

At the end of the day, Cortelezzi says, for each option, the weight loss is typically a result of calorie restriction. Specifically, time-restricted feeding’s benefit is it limits snacking. “If you have trouble with snacking in the evening,” Cortelezzi says, “setting an end time, like not eating after 8 p.m., that can help people cut down on snacking which can add those extra calories.”

Noting this approach focuses more on when you’re eating rather than what you’re eating, Cortelezzi explains it doesn’t require much counting when it comes to calories or macronutrients, “so it can be a little simpler approach if you’re having trouble with that day-to-day calorie tracking.” 

Besides weight loss, Cortelezzi says research indicates other potential benefits such as improved blood sugar levels, reduced insulin resistance and lower cholesterol levels, triglycerides, blood pressure and inflammation.

while intermittent fasting, it’s important to make the most out of the time you’re eating.

“That’s not saying, ‘Eat everything you can,’ but making the most as far as choosing a well-balanced diet,” Cortelezzi says. “Choose nutrient-rich foods that are going to help give your body the nutrients and fuel that it needs to stay healthy.”

Listing lean proteins, vegetables, fruits and whole grains, Cortelezzi says, “Those things are all going to give you the nutrients you need but also help you fill up and keep your calories in a good range.”

Noting it can be hard for people to remember to drink if they’re not eating, Cortelezzi says it’s important to stay hydrated if fasting.

Some of this content originally appeared in Balanced Family Magazine

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