Just the thought of fasting may make you hungry. But going without food for a time — whether for health or religious reasons — can be good for you, says Nizar Zein, MD, Director of the Mikati Center for Liver Disease and Transplantation.
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“There’s actually a range of ways to fast,” he says. “Sometimes fasting means avoiding certain types of food, like carbohydrates or fats. Other times it just means reducing calories overall. Then there’s the type of fasting when you don’t eat (or sometimes drink) at all for a day or more.”
Many religions promote some form of fasting as a spiritual discipline. And medical literature indicates fasting, in general, can:
- Stimulate weight loss.
- Decrease inflammation from chronic conditions like arthritis.
- Improve blood pressure.
- Reduce cholesterol.
“There also are theories that periodic fasting may help you live longer, boost brain function and prevent neurodegenerative disease,” says Dr. Zein.
What to know before you start
If you’re planning a fast in which you don’t eat at all, Dr. Zein recommends these five tips for maintaining your health and energy level.
- Ease into it. Cut back on food and drink gradually for several days — or even weeks — before your fast. Otherwise, abruptly beginning a fast will be a shock to your body. “Do not eat three full meals a day with between-meal snacks and then suddenly stop eating one day,” says Dr. Zein. “If your body is used to regular refueling, you may have a hard time maintaining energy levels during a fast.”
- Avoid sugary foods and drink. Loading up on cookies and sweet tea before your fast isn’t a good idea. You may feel full and satisfied at first, but when your blood sugar plummets an hour or two later, you may become extremely hungry and weak. To have enough energy for the long haul, fill up on complex carbohydrates (like pasta, rice and potatoes) and protein (like meat and beans).
- Cut down on activity. “It’s not a good idea to do intense exercise when you’re not eating or drinking,” says Dr. Zein. “If you’re not planning to replenish nutrients for a while, preserve your energy for vital daily activities.”
- Plan ahead for medications. Before fasting, talk to your doctor about how to take your medications. Some medications — such as for seizure disorders — are essential, and you shouldn’t fast from them. Other medications — such as some antibiotics — should be taken with food. “When people have adverse outcomes from fasting, it’s often because they didn’t take their medications correctly,” says Dr. Zein.
- Ease out of it. At the end of your fast, replenish your calories gradually. Rather than going on an eating binge right away, spread those calories over your next two meals. This is better because it will help you avoid rapid changes in blood sugar and the fatigue associated with consuming a large amount of food.
Even when following these tips, too much fasting can be dangerous. Don’t abstain from all food and drink for longer than a few hours, says Dr. Zein. Fasting for too long may cause dehydration, mental stress and disrupted sleep.
Who shouldn’t fast?
“Overall, fasting can be a healthy practice. I recommend it,” says Dr. Zein. “However, it can cause problems for people with certain health conditions.”
Those who should not fast from all food and drink include people who:
- Have diabetes and struggle with keeping blood sugar stable.
- Have chronic kidney disease.
- Are breastfeeding.
- Are underweight.
- Are recovering from surgery or illness.
Otherwise, fasting may provide psychological and physical benefits when done a healthy way. Talk with your doctor before making it part of your routine.