Do’s and don’ts of intermittent fasting

Clock on a plate with fork and knife.
Research suggests that intermittent fasting is associated with weight loss, improved cholesterol, blood sugar control and decreased inflammation. (Getty/iStockphoto/everydayplus)

Intermittent fasting involves cycling between periods of eating and fasting.

Proponents say intermittent fasting is a safe and effective way to lose weight and improve your health. “Intermittent fasting is an umbrella term for an eating pattern that includes periods of fasting and non-fasting over defined periods of time,” says Anna Kippen, a registered dietitian with the Cleveland Clinic. “There are different forms of intermittent fasting.”

One of the more popular approaches is called time-restricted eating. It calls for eating only during an eight-hour window, and fasting the remaining 16 hours of the day. “It can help to decrease our calories but also allows our gut and hormones the ability to rest between meals during our ‘fast,'” Kippen says.

Another popular approach is the 5:2 plan, in which you follow a normal, healthy meal pattern for five days a week. The other two days a week, you consume only one meal of between 500 and 700 calories each day. “This allows our body to rest as well as cut down on calories we consume as a whole throughout the week,” Kippen says.

[See: Foods That Can Support Your Immunity.]

Research suggests that intermittent fasting is associated with weight loss, improved cholesterol, blood sugar control and decreased inflammation.

“Preclinical and clinical trials have shown that intermittent fasting has broad-spectrum benefits for many health conditions, such as obesity, (diabetes), cardiovascular disease cancers and neurologic disorders,” according to a study published in the New England Journal of Medicine in 2019. Clinical research has focused primarily on overweight young and middle-aged adults, the study says.

Whatever method of intermittent fasting you choose, it’s important to apply the same fundamental nutrition principles to intermittent fasting as to other healthy eating plans, says Ryan Maciel, a registered dietitian and head nutrition coach for elite athletes and organizations for Precision Nutrition. The company provides nutrition education and tools to health and fitness professionals and individual clients in 120 countries. Maciel is based in Cambridge, Massachusetts.

“In fact, these (principles) may be even more critical since you are going for more extended periods without food, which can result in overeating for some people,” Maciel says.

Here are principles you should adhere to if you’re on an intermittent fasting regimen:

— Consume minimally processed foods most of the time.

— Eat a balance of lean protein, veggies, fruits, smart carbs and healthy fats.

— Create flavorful, delicious meals that you enjoy.

Eat your meals slowly and mindfully, until you’re satisfied.

Intermittent fasting diets don’t mandate specific menus. However, adhering to good eating principles, there are certain types of foods it’s best to consume and avoid.

Here are three foods to eat on an intermittent fasting diet:

— Lean proteins.

— Fruits.

— Vegetables.

Lean Proteins

Eating lean protein keeps you feeling full longer than consuming other foods and will help you maintain or build muscle, Maciel says.

Here are five lean, healthy protein sources:

— Chicken breast.

— Plain Greek yogurt.

— Beans, peas and lentils.

— Fish and shellfish.

— Tofu and tempeh.

[See: 7 Proven Health Benefits of Blueberries.]


As with any eating regimen, it’s important to consume highly nutritious foods while intermittent fasting. Fruits and vegetables are typically packed with vitamins, minerals, phytonutrients (plant nutrients) and fiber. These vitamins, minerals and nutrients can help lower cholesterol levels, control blood sugar levels and maintain bowel health. Another plus: fruits and vegetables are low in calories.

The government’s 2015-20 Dietary Guidelines for Americans recommend that for a 2,000-calorie-a-day diet, most people should eat about 2 cups of fruit on a daily basis.

Here are 10 healthy fruits to consume during intermittent fasting:

— Apples.

— Apricots.

— Blueberries.

— Blackberries.

— Cherries.

— Peaches.

— Pears.

— Plums.


— Watermelon.


Vegetables can be an important part of an intermittent fasting regimen. Research shows that a diet rich in leafy greens may reduce your risk of heart disease, Type 2 diabetes, cancer, cognitive decline and more. The government’s 2015-20 Dietary Guidelines for Americans recommend that for a 2,000-calorie-a-day diet, most people should eat 2.5 cups of vegetables on a daily basis.

Here are six vegetables that would be good to consume as part of a healthy intermittent eating regimen:

— Kale.

— Spinach.

— Chard.

— Cabbage.

— Collard greens.

— Arugula.

Foods to Avoid

There are certain foods that aren’t good to consume as part of an intermittent fasting regimen. You should stay away from foods that are calorie-dense and contain high amounts of sugar, fat and salt. “They won’t fill you up after a fast, and can even make you hungrier,” Maciel says. “They also provide little to no nutrients.”

To maintain a healthy intermittent eating regimen, avoid these foods:

— Snack chips.

— Microwave popcorn.

You should also avoid foods that are high in added sugar. Sugar that comes in processed foods and drinks is devoid of nutrition and amounts to sweet, empty calories, which is not what you’re seeking if you’re fasting intermittently, Maciel says. “They will make you hungry since the sugar metabolizes super-fast,” he says.

[See: The Best Diet for Your Personality.]

Sugary foods to avoid if you’re engaging in intermittent fasting include:

— Cookies.

— Candy.

— Cakes.

— Barbecue sauce and ketchup.

— Fruit juice.

— Sugary cereals and granola.

More from U.S. News

Keto-Friendly Vegetables

Foods for Diabetes

The Best Foods to Prevent and Manage Diabetes

Intermittent Fasting: Foods to Eat and Avoid originally appeared on

Federal News Network Logo

More from WTOP

Log in to your WTOP account for notifications and alerts customized for you.

Sign up