Intermittent Fasting Tested: Alternate Day Fasting vs. 5:2 Diet vs. Time-Restricted Eating

What form of intermittent fasting is the best: alternate day fasting, the 5:2 diet, or time-restricted eating?

What form of intermittent fasting is the best: alternate day fasting, the 5:2 diet, or time-restricted eating?

Intermittent fasting, which comes in several types, causes mild to moderate weight loss, reduces blood pressure, blood sugar levels, triglyceride and cholesterol levels.

This pattern of eating can improve microbial gut diversity and help people eat less throughout the day.

But which is the best type of intermittent fasting?

A group of researchers reviewed 25 studies on three forms of intermittent fasting:

  • Time-restricted eating: an eating window of 8 to 12 hours and fasting during the remaining hours each day.
  • 5:2 diet: five days eating normally and two days fasting with restricting the food intake to 500 calories.
  • Alternate day fasting: fasting on every other day with restricting the food intake to 500 calories.

The studies reported that those who follow a time-restricted eating regime noticed 3 percent weight loss.

While alternate day fasting produced 3 to 8 percent weight loss within three to eight weeks.

The weight loss results for the 5:2 diet group are similar to alternate day fasting, the finding is surprising as people on the 5:2 diet fasted much less than those who did alternate-day fasting.

The 5:2 diet and alternate day fasting produces similar weight loss results to regular dieting such as low-calorie diets.

Professor Krista Varady, the study’s first author, said:

“We noted that intermittent fasting is not better than regular dieting; both produce the same amount of weight loss and similar changes in blood pressure, cholesterol and inflammation.”

Moreover, people on any of these two intermittent fasting regimens have been found to maintain 7 percent weight loss over a year.

Professor Varady said:

“You’re fooling your body into eating a little bit less and that’s why people are losing weight.”

The review includes some practical advice for individuals who may consider an intermittent fasting regimen.

Side-effects, such as dizziness, constipation, and headaches will drop within one or two weeks of fasting.

Drinking more water can reduce headaches due to dehydration.

  • Exercise: Moderate to high-intensity activity is possible as some participants reported that exercise gives them more energy during the fasting hours. Though, it is recommended to have the fasting meal after exercise.
  • What to eat: Make sure you eat fruits, vegetables and whole grains as they are high in fibre, which eases constipation.
  • Avoid alcohol and caffeine: Alcohol and caffeinated energy drinks are high in calories and can cause headaches due to dehydration.
  • Who should avoid fasting: Those with a BMI less than 18.5, those with eating disorders, those who need to take their medicine with a meal at regular times, children under 12, pregnant or lactating women, and shift workers.

Professor Varady said:

“People love intermittent fasting because it’s easy.

People need to find diets that they can stick to long term.

It’s definitely effective for weight loss and it’s gained popularity because there are no special foods or apps necessary.

You can also combine it with other diets, like Keto.”

About the author

Mina Dean is a Nutritionist and Food Scientist. She holds a BSc in Human Nutrition and an MSc in Food Science.

The study was published in the Annual Review of Nutrition (Varady et al., 2021).

Get FREE email updates to PsyBlog

Hello, and welcome to PsyBlog. Thanks for dropping by.

This site is all about scientific research into how the mind works.

It’s mostly written by psychologist and author, Dr Jeremy Dean.

I try to dig up fascinating studies that tell us something about what it means to be human.

Get FREE email updates to PsyBlog. Join the mailing list.