The Beginner’s Guide to Intermittent Fasting

By Alyssa Kessel, RDN, LD, Expert Dietitian

Intermittent fasting is one of the world’s most popular health and fitness trends right now. People are not only using it to lose weight, but to improve their health and simplify their lifestyles. I’ve received a lot of questions about this in recent patient visits, so I decided to discuss it here for anyone looking to get started. Let’s jump in!

What is intermittent fasting?

First, intermittent fasting is NOT a diet; it’s a lifestyle choice or pattern of eating that cycles between eating and fasting phases. It’s more about when you eat vs. what you eat.

Where did fasting come from?

Even though it’s a trend right now, intermittent fasting has been around for centuries as part of human evolution. People have even fasted for spiritual and religious reasons.

More recently, this topic has gained interest because of its effects on body weight and reduction of body fat. A recent study by USC found that participants that followed this fasting had a reduced risk of developing cancer, heart disease, diabetes, and other age-related risks.

For more reading on the science behind fasting, I recommend reading these articles and studies:


How does fasting help weight loss?

During fasting, your body uses your own stored fat for energy. This happens because of lowered insulin levels, increased growth hormones, and increased norepinephrine in your body. All of these hormone changes cause your body to increase your metabolism, which can help with weight loss, body fat reduction, and increased muscle mass.

This all happens after 12 hours of fasting, when your body enters a fat-burning state. Most people are going to take advantage of their natural sleep cycle. After dinner the night before, they’re going to stop eating around 6 pm and use the overnight hours to get their fasting started.

How do you start fasting?

Fasting is very flexible; you get to choose which days you fast and how many hours you want to fast. I recommend you start slowly and work yourself up to a longer fasting interval. Again, overnight is easier, so if you are going to fast, skip breakfast the next morning and stretch it out an extra hour or two to see how long your fast can last.

What are the easiest fasting methods?

There are two popular methods of intermittent fasting:

16-8 Method

This is the most popular method today. The idea is that you will be fasting for 16 hours, and then eating during an 8-hour window throughout the day. For example, if your last meal of the day is around 7 pm, you would fast until 11 am. This overnight fast would help you complete a 16-hour fast. Then, at 11 am, you would start your 8-hour window of eating.

It’s important that you still eat all of your calories and nutrients for the day. You do not decrease the amount of calories consumed; you simply eat them in a shorter time window.

I recommend trying the 16-8 method first, and picking 2-3 days each week to fast.

fastingEat-Stop-Eat Method

This method is a 24-hour fast. If you eat dinner at 7 pm, you would fast until 7 pm the next day. It’s important that when you break the fast, you do it with a normal-size, high-nutrition meal. The next day, your body may need more calories. In this case, I would recommend increasing your calorie intake with an additional protein-based snack.

Unlike the 16-8 method, the Eat-Stop-Eat method is only recommended for 1-2 days a week, because of the longer fasting period.

Additional Tips

  • Make sure you’re not reducing your calorie intake for the day. You should still be getting the recommended amount of calories in your shorter window.
  • Drink water! It’s okay to drink coffee or black tea during your fasting window, but you should still drink plenty of water to stay hydrated.
  • Try following a lower carbohydrate diet so your body will burn more stored fat.
  • Fasting is not recommended for: people with a history of eating disorders; women who are pregnant or breastfeeding; people under the age of 18.

At the end of the day, there’s no one size fits all nutrition solution. You should focus on what works best for your body to live a healthy lifestyle. If you have any questions about intermittent fasting or would like to incorporate it into your meal planning, please call us at 513-791-9474 to set up a consultation.

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