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What Is Intermittent Fasting?

Myles Spar, MDIntermittent fasting is a term used to describe meal-time schedules that include regular periods of voluntary fasting over a given period. Myles Spar, MD, a Diplomate of the American Board of Integrative Medicine (ABOIM), says intermittent fasting is suitable for virtually anyone because it’s simple, and people who have had limited success with other dietary regimens over the years may find intermittent fasting much easier to follow.

Many people fasting intermittently will abstain from food 16 hours every day. They may skip breakfast, eat a regular lunch, and stop eating at 8 p.m. Others prefer 24-hour periods of fasting, perhaps twice a week. Whichever method they adopt offers several benefits, Dr. Spar says.

Perhaps the most noticeable is weight loss, but intermittent fasting also serves as an effective daily detox. That’s because it prompts the body to use fat rather than blood sugar as a source of fuel. This makes the body more efficient, which is good for longevity. When your body lacks enough resources to fuel junk cells, it goes through autophagy, or cellular cleansing. Through this mechanism, the body gets rid of damaged cells and unnecessary or dysfunctional cellular components. This explains why intermittent fasting can also deliver anti-inflammatory benefits, helping to control processes that can lead to disease.

Although intermittent fasting is safe, Dr. Spar says everyone should consult a medical professional before doing it. He doesn’t recommend it for teens and children, who are still growing. People with low-blood sugar or diabetes can also fast intermittently, he says, but they should work with their health care practitioner during the process. They may need to adjust their insulin intake because intermittent fasting lowers insulin levels in the body. Interestingly, it may also reduce the amount of medication or insulin needed, and has been shown to reverse diabetes in some people.

People can still exercise safely while intermittently fasting. Exercising right after a 16-hour fast is ideal for weight loss, Dr. Spar says, because the body will start burning fat immediately. But he doesn’t recommend combining an intermittent fast with endurance training, such as for an Ironman or marathon. Training for those events requires a constant supply of energy.

According to Dr. Spar, there are no contraindications for intermittent fasting.
“Go by how you feel,” he says. “If you feel dizzy or lightheaded, try 12 hours of fasting instead of 16. Your plan needs to be individualized. For instance, some people can’t exercise while intermittent fasting.”

The biggest advice he has for people adopting a schedule of voluntary fasting is to eat regular portions. “Don’t compress all of the eating you would have done in a 24-hour period into eight hours. That only defeats the purpose.”

If you would like to learn about integrative medicine board certification, contact the ABOIM, a Member Board of the American Board of Physician Specialties® (ABPS).