You’ve heard of intermittent fasting, but is it for you?

Many Americans have gained weight during the Covid pandemic. According to a poll conducted in February 2021 by the American Psychological Association, 42 percent said they had undesired weight gain, with an average gain of 29 pounds (37 pounds for men vs. 22 pounds for women).

Some people who have been unsuccessful with their usual diets have been looking at a completely different approach called intermittent fasting, sometimes abbreviated IF. Instead of focusing on what to eat, IF focuses on when food is consumed and restricted. To better understand this method, I consulted medical journals and interviewed Geri Wohl, a local, certified nutrition consultant and educator.

Wohl explains there are three main types of IF.

The most common pattern of IF is to restrict eating to an eight-hour window, say from noon to 8 p.m. (known as the 16/8 method or “Leangains” protocol). Many people who adhere to this regimen feel better and have more energy.

Other methods of IF are the following: once or twice per week not eating for 24 hours (known as the “eat stop eat” method), or two days a week on non-consecutive days eating only 500 to 600 calories (the 5:2 diet).

While no food is allowed during a fast, non-caloric beverages are permitted, such as water, tea or coffee. Because most people end up consuming fewer calories, IF usually results in weight loss.

Aside from weight loss, IF appears to have additional benefits. Okinawans on Japan’s Ryukyu Islands are well known for their extreme longevity. They practice intermittent fasting and have low rates of obesity and diabetes.

One of the main benefits of IF, particularly when combined with regular exercise, is improved insulin sensitivity. (Poor insulin sensitivity or insulin resistance results in glucose being unable to enter cells. This leads to a high blood-glucose level, and when the level surpasses a certain threshold, the condition is called type 2 diabetes.) IF also improves the microbiota (gut bacteria), reduces abdominal fat and aids in disease resistance.

Intermittent fasting, when it leads to calorie reduction, can be good for brain health. In a study looking at 50 normal-to-overweight people with a mean age of 60.5, calorie restriction of 30 percent for three months resulted in 20 percent improvement in verbal memory scores compared to controls. In another study, 220 non-obese healthy adults who decreased their calories by 25 percent showed improved memory after two years compared to controls.

IF has been shown to have positive effects on cardiovascular health. Improvements have been found in blood pressure, resting heart rate, HDL (“good cholesterol”), LDL (“bad cholesterol”), triglycerides, glucose and insulin. When study participants followed IF, these indicators improved after only two to four weeks.

Cancer treatment trials utilizing IF are in progress. The theory is that IF may impair the growth of cancer cells and increase their sensitivity to chemotherapy and radiation. Case studies involving patients with glioblastoma (a kind of brain cancer) indicate IF can suppress tumor growth and improve survival.

In neurodegenerative disorders such as Alzheimer’s disease and Parkinson’s, there are animal models of these diseases that show that alternate-day fasting delays the onset and progression of disease. Multiple sclerosis patients who adhered to an IF regimen had reduced symptoms within two months.

In asthmatic patients who followed an alternate-day fasting regimen, their symptoms improved over a two-month period.

There also appears to be some evidence that IF followed by eating a vegetarian diet helps those with rheumatoid arthritis.

Another benefit of IF is heightened spirituality — think of Catholic, Muslim and Jewish fasting traditions. As Wohl states, “Fasting provides a reset for our body and mind.”

Who should not follow IF? Pregnant women, diabetics and people who take certain medications which have to be timed with eating. IF should also be avoided in the 25 percent of obese people who are binge eaters.

Although the effects of intermittent fasting on our body are not completely understood, there does appear to be a broad-spectrum benefit for many health conditions. If you are contemplating starting an IF plan, check with your doctor first and consult with a nutritionist.

In many of these IF studies, the dropout rate has been high, so be forgiving to yourself if you’re not 100 percent compliant. If you are successful in following intermittent fasting, I predict your golden years could be sparkling.

Dr. Jerry Saliman

Jerry Saliman, MD, retired from Kaiser South San Francisco after a 30-year career and is now a volunteer internist at Samaritan House Medical Clinic in San Mateo.