The Do's and Dont's of Intermittent Fasting

Is intermittent fasting right for you?

Medically reviewed in January 2020

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Fasting isn’t a new concept—many religions have practiced it for centuries. But intermittent fasting has become increasingly popular in the health and fitness worlds as a way to lose weight and improve overall wellness. Some preliminary studies suggest it may help reduce the risk of diabetes, heart disease and certain cancers. Read on to see if fasting is right for you—and how to do it safely. 

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DO: Make a Plan

Intermittent fasting has different options—from skipping one or two meals a day, to reducing your daily calories by 75%, to consuming nothing but water for 16 to 36 hours. Talk with your doctor before you begin, and decide together what makes the most sense for you. 

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DON’T: Fast With a Health Condition

Fasting isn’t for everyone, especially those with chronic illnesses or a history of eating disorders, according to Anne Brock, RDN, LD specializing in weight loss and diabetic education at West Valley Medical Center in Caldwell, Idaho. In addition to people with type 1 and 2 diabetes, children, teens and pregnant or nursing women should avoid intermittent fasting. 

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DON’T: Overindulge the Night Before

The day before starting a fast, avoid overindulging in a fatty but filling meal like a burger and fries. Instead, fuel your body with slow-burning nutrients. “Get some carbohydrates, protein and unsaturated fats to ensure you’re getting nutrient-dense foods, rather than a high-fat meal right before fasting," suggests Brock.

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DO: Drink Lots of Water

Proper hydration is key during a fast--and can help curb hunger. In addition to drinking water, you’ll need to replace the hydration you'd normally receive from water-dense foods. Still feeling those hunger cues? Sip plain tea, black coffee, diet soda or another low-calorie drink to keep the stomach from feeling too empty.   

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DON’T: Work Out Too Hard

You'll want to avoid any high-intensity workouts during a fast, but light to moderate exercise may actually be beneficial. “In one study, eating 20% to 25% of [participants’] calories for two days per week, combined with moderate exercise, resulted in superior weight loss compared to fasting or exercising alone,” says Brock. “But it’s important to make sure you’re getting 25% of your daily calories, so you don’t deplete muscle mass.”

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DO: Listen to Your Body

Intermittent fasting affects everyone differently, so it’s important to listen to your body. If you feel dizzy or weak, or if your fast is affecting your ability to complete everyday functions, stop. According to Brock, “It’s important for people to keep in mind that they may feel fatigued, irritated, distressed, depressed and confused on fasting days.”

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