Everything you need to know about intermittent fasting

Alyssa Bradford
·4 min read
Customers check prices while shopping at a grocery store in Wheeling, Ill., Saturday, Jan. 27, 2024.
Customers check prices while shopping at a grocery store in Wheeling, Ill., Saturday, Jan. 27, 2024. | Nam Y. Huh

Research on the benefits of intermittent fasting is conflicting.

A recent study, with only the abstract released by by the American Heart Association, found that intermittent fasting could cause an increased risk of death.

However, other studies found improvement in inflammatory diseases, per Mayo Clinic. Here’s what you should know.

What is intermittent fasting?

Intermittent fasting is an eating plan where an individual goes from fasting to eating on a regular schedule, per Johns Hopkins Medicine.

Medical News Today lists different plans people follow:

  • 12/12: eating for 12 hours and fasting for 12 hours.

  • 16/8: eating for eight hours and fasting for 16 hours.

  • 5/2: eating regularly for five days a week and limiting yourself to one 500 to 600 calorie meal the other two days.

  • Alternative day fasting: eating every other day or limiting yourself to 500 calories every other day.

  • A weekly 24-hour fast: fasting one day a week.

According to Mayo Clinic, side effects of intermittent fasting may include:

  • Fatigue.

  • Insomnia.

  • Headaches.

  • Hunger.

  • Nausea.

The benefits of intermittent fasting

Research has shown benefits of intermittent fasting includes improvement or reduces risk of:

In a 2023 study published by the National Library of Medicine, researchers found intermittent fasting to be an easy and safer alternative to calorie restriction. Improvements were found in the body’s glucose and lipid profiles, weight levels and inflammation.

Animal studies have shown intermittent fasting improves diseases such as obesity, diabetes, cardiovascular disease, cancers and neurodegenerative brain diseases, all chronic disorders, per The New York Times.

The health risks or problems associated with intermittent fasting

Some health risks or problems associated with intermittent fasting go against the benefits found in other research.

According to a 2024 study’s abstract, published by the American Heart Association:

  • Eating all meals within less than eight hours per day led to a 91% higher risk of dying from heart disease.

  • Among those with existing heart issues, eating for at least eight but less than 10 hours daily raised the risk of heart disease or stroke death by 66%.

  • Time-restricted eating did not lower the overall risk of death from any cause.

Per a 2023 study published in the Journal of the American Heart Association, time-restricted eating was not a strategy for long-term weight loss.

Wendy Bennet, an associate professor of medicine at Johns Hopkins University School of Medicine and co-author of the above study, told Live Science that recent research suggests a need to examine the “fad diet push that people should be doing time-restricted eating.”

Trista Best, a registered dietitian at Balance One Supplements, told Healthline that risk of intermittent fasting could stem from possible metabolic changes and eating habits.

“Restricting food intake to an eight-hour window could lead to overconsumption during the eating period, especially if individuals compensate by indulging in larger meals or unhealthy foods. This may contribute to metabolic dysregulation, including insulin resistance, elevated blood sugar levels and increased inflammation, all of which are risk factors for cardiovascular disease.”

Johns Hopkins Medicine found health problems rose for individuals who fasted in these categories:

  • Those under the age of 18.

  • Pregnant or breastfeeding women.

  • Type 1 diabetics.

  • Those with a history of eating disorders.

In general, what is a healthy diet to follow?

While not ruling out intermittent fasting completely and noting both the pros and cons, Karishma Patwa, a cardiologist with Manhattan Cardiology in New York City, suggests the Mediterranean-DASH, or MIND, diet, per Healthline.

According to Harvard T.H. Chan School of Public Health, the Mediterranean-DASH diet includes:

  • At least three servings a day of whole grains.

  • At least one serving of vegetables, other than leafy greens, a day.

  • At least six servings of leafy green vegetables a week.

  • At least five servings of nuts a week.

  • At least four meals that have beans a week.

  • At least two servings of berries of week.

  • At least two meals of poultry a week.

  • At least one meal that includes fish a week.

  • Use olive oil if adding fat.

Before trying any diet, including intermittent fasting, talk to your doctor, per Johns Hopkins Medicine.