Intermittent Fasting: A Beginner's Guide on How to Start

Medically Reviewed on 5/19/2022

What is intermittent fasting?

Intermittent fasting is a diet where you avoid food for a set interval and eat during a specific time window. Start intermittent fasting by talking to your doctor, considering your lifestyle, planning healthy meals and exercise, and being aware of side effects.
Intermittent fasting is a diet where you avoid food for a set interval and eat during a specific time window. Start intermittent fasting by talking to your doctor, considering your lifestyle, planning healthy meals and exercise, and being aware of side effects.

Intermittent fasting is an eating method that alternates between "feast" and "famine." You avoid food for a set interval and eat during a specific time window. While many people struggle to imagine themselves deliberately skipping meals, intermittent fasting has become more popular over the last several years. Often touted as a weight-loss "magic pill" as well as a treatment for a host of diseases, including type 2 diabetes and heart disease, you may wonder if intermittent fasting could be a good fit for you.

Read on to learn more about how to start intermittent fasting.

Intermittent fasting, also called time-restricted eating, is the practice of intentionally fasting for extended periods. Fasting for extended periods lowers insulin levels and lets the body tap into fat stores. Your liver runs out of glycogen stores after about 12 hours, so fasting longer than this forces your body to use stored fat for energy, which can lead to improved metabolic function and loss of excess weight. 

There are two basic methods of intermittent fasting: fasting (or consuming very few calories) on specific days of the week or fasting for a significant part of each day, leaving an "eating window," which is the only time you consume food. 

Common methods of intermittent fasting include:

  • The 16:8 method: fasting for 16 hours and eating during an 8-hour window, such as fasting between 7:00 p.m. and 11:00 a.m. 
  • The 5:2 method: fasting for two days a week or limiting yourself to a single small 500-600 calorie meal two days a week.
  • One meal a day or the 23:1 method: consuming one meal a day until satiated, usually fasting for 23 hours a day with a one-hour eating window. 
  • Alternate day fasting: fasting or limiting yourself to a single small meal every other day. 

Intermittent fasting can lower your calorie intake while reducing cravings for unhealthy foods and can train your body to feel full after a smaller meal.

Who benefits from intermittent fasting?

People struggling with obesity, type 2 diabetes, heart disease, sleep apnea, high blood pressure, and other weight-related diseases may benefit from intermittent fasting. There's some evidence that intermittent fasting may help people with inflammatory conditions such as arthritis and multiple sclerosis.

Research has shown additional benefits to intermittent fasting that apply more generally, including: 

Who should avoid intermittent fasting?

Intermittent fasting is generally safe but isn't appropriate for everyone. You should always speak with your doctor before making a significant dietary change, especially if you take any medications. People who should generally avoid intermittent fasting include:

How can I start intermittent fasting?

If you want to try intermittent fasting, there are some steps you should take to make sure you start safely.

Talk to Your Doctor

It's best to talk with your primary care provider when you make a restrictive diet change. This is especially true for people who take medication, as your dose may need to be adjusted. You may still need to take your medication with food, even on fasting days. Your doctor can give you specific advice for your unique situation. 

Consider Your Lifestyle 

When deciding what intermittent fasting method might be right for you, consider what times of the day it's already easy for you not to eat. For example, if you work 9-5, it may be easiest to follow a 16:8 method where you skip breakfast, have lunch at work, and stop eating right after dinner. 

Plan Healthy Meals

When you practice intermittent fasting, you will need to eat healthy, high-nutrient foods during your eating windows. While your doctor can help point you toward good food choices, a Mediterranean-style diet is healthy for most people.

Stay Hydrated

Don't forget to drink while you fast. Calorie-dense drinks like milk, juice, or soda are not allowed while fasting, but water and zero-calorie drinks like herbal tea are. 

Plan Movement Into Your Day

Movement and exercise are still important for building muscle and maintaining cardiovascular health. If you have less energy during your fasting window, plan more strenuous activities after meals. Stick to gentler forms of movement, like walking or yoga, during fasting periods.

Be Aware of Side Effects

Side effects of intermittent fasting can include headaches, fatigue, nausea, and hunger. You can reduce the severity of side effects by easing into an intermittent fasting routine and gradually increasing your fasting window over time. If you feel sick or weak while fasting, contact your doctor and consider breaking your fast.

Intermittent fasting can be an excellent tool for people struggling with their weight or with some chronic diseases. Despite the restriction of fasting times, many people find that it's easier to follow than methods like calorie counting, which require measuring and logging your food intake. Remember that intermittent fasting is just one option for weight control, and it's not the right fit for everyone. If you find intermittent fasting too difficult, your doctor or nutritionist can help you adjust your fasting plan or find another weight loss plan that's a better fit for you.  


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Medically Reviewed on 5/19/2022

Cleveland Clinic: "Intermittent Fasting: How It Works and 4 Types Explained."

John Hopkins Medicine: "Intermittent Fasting: What is it, and how does it work?"

Mayo Clinic: "What is intermittent fasting? Does it have health benefits?"

UCLA Health: "Health benefits of intermittent fasting (and tips for making it work)."