Intermittent fasting may improve cholesterol levels, how we metabolize glucose and burn fat, and even cognitive function. (For Spectrum Health Beat)

If you’ve tried intermittent fasting or you know someone who has, you’re part of a growing trend.

According to the International Food Information Council, intermittent fasting became the No. 1 diet among Americans in 2020.

But is this skyrocketing popularity an indication that intermittent fasting works? Or just that homebound Americans are increasingly desperate to shave off the “Quarantine 15”?

“I think it’s a little bit of both, to be honest,” said Kathryn Francisco, a registered dietitian nutritionist at the Spectrum Health Women’s Health & Wellness Center.

“On the one hand, we have research that shows intermittent fasting may offer health benefits like decreasing insulin resistance and optimizing metabolism,” Francisco said. “We’ve also seen an increase in the number of people who say they’re dissatisfied with their weight and who want to establish healthier eating habits.”

What is it?

Fasting is intentionally abstaining from food for a set period of time. There are several different ways to do intermittent fasting, but they are all based on choosing regular time periods to eat and fast.

For instance, you might eat only during an eight-hour period each day and fast for the remainder. Or you may choose to eat only one meal, once or twice a week.

The benefits

According to studies, intermittent fasting may improve cholesterol levels and how we metabolize glucose and burn fat.

It may even improve cognitive function. In animal studies, brain functioning and brain shape changed in experimental groups practicing intermittent fasting—in ways potentially protective against Alzheimer’s disease and Parkinson’s.

Intermittent fasting also promotes cellular responses that contribute to lower levels of inflammation and oxidative stress.

How it’s done

Intermittent fasting isn’t for everyone. Those with insulin-dependent diabetes should avoid fasting, as should anyone with a nutrient deficiency (low iron, for example).

It should also be avoided by athletes in training, women who are pregnant or breastfeeding, those with a history of an eating disorder and those younger than 18.

If none of these caveats applies to you and you’d like to try intermittent fasting, the Spectrum Health Women’s Health and Wellness Center recommends talking to your doctor to discuss any risks you might need to be aware of.

Then, if you do go ahead, take it slow.

To begin, simply increase the amount of time between dinner and breakfast.

Waiting at least 12 hours between dinner and breakfast every day or every other day has been shown to improve weight loss and metabolism.

If this goes well, you may also want to experiment with gradually expanding your daily fasting period to 16 hours of fasting and eight hours of eating.

Another form of intermittent fasting is the 5:2 approach. On this schedule, you would eat as you normally would 5 out of 7 days per week. On the other 2 days, you would fast except for 1 meal which contains 500-600 calories. It is important to maintain adequate hydration throughout the day.

Some helpful do’s

  • Choose nutritious foods, including whole grains, leafy greens and lean proteins. These help keep your blood sugar levels steady and allow you to feel full longer.
  • Stay hydrated—sip on water, black coffee and tea throughout the day.
  • Keep yourself busy with low-intensity activities such as walking or yoga, or relax with a book, podcast or bath. Boredom can often trigger unintended snacking.
  • Continue to take your daily vitamins and any medications. Supplements are especially important during fasting to make sure your body gets the nutrients it needs.

Some helpful don’ts

  • Don’t try to fast too much too soon. Ease into your new fasting routine and give your body time to adjust to a new eating pattern.
  • Don’t do high-intensity workouts as you adjust to your fasting or on your “fast day,” as this can limit your ability to maintain your fast.
  • Don’t worry if you occasionally miss a fast day here and there. A 12- or 16-hour occasional fast is still beneficial for your body.