For millennia, people have fasted to increase spiritual awareness. Now, evidence is mounting that intermittent fasting might be good for the body as well as the mind and soul.
A simple 24-hour fast can restore the body's ability to regenerate intestinal stem cells as we age, according to a study by biologists at the Massachusetts Institute of Technology.
Such cells are the source of all new intestinal cells. So, fasting might help people recover better from gastrointestinal infections or other intestinal conditions.
Earlier research has found that people who reduce their overall caloric intake might enjoy longer lifespans.
But before you take on the eating habits of a monk or yogi, understand both the potential benefits and risks of doing so, says Lisa Cooper, a registered dietitian with Orlando Health in Florida.
The potential health benefits of fasting
For starters, don’t rush to conclude that intermittent fasting is guaranteed to boost your health.
Such fasting typically is defined as a complete or partial reduction in calories for a set number of days per week, or for a set amount of time within 24 hours.
Cooper says the data remains inconclusive about whether fasting improves a person’s general health.
“More clinical trials are needed to determine the long-term risks or benefits, especially with regard to the impact on chronic diseases like diabetes, heart disease, cancer or Alzheimer’s,” Cooper says.
Still, animal studies – such as the MIT research, which focused on mice -- are promising.
“There is strong evidence in animal research that intermittent fasting shows improvements in chronic diseases like diabetes, heart disease and stroke,” Cooper says.
Some specific benefits to human health also are clear. “Weight loss is one of the benefits of fasting because of the calorie restriction,” Cooper says. Such weight loss can reduce your overall body fat and lower blood pressure.
The potential risks of fasting
While fasting might offer benefits, it also is not for everybody, Cooper says.
“Fasting would not be appropriate for people who require extra calories or nutrients for growth and development,” she says.
This includes children and adolescents, as well as women who are pregnant or breastfeeding.
Some people with specific health conditions would not be good candidates for fasting. They include those with eating disorders, diabetes and hypoglycemia, or those who are underweight. Also, you should not fast if you require food to be taken with medications.
Some people may experience health symptoms when they fast. These might include:
- Increased hunger
- Hypoglycemia/low blood sugar
- Light headedness
How to fast properly
It is difficult to nail down hard-and-fast rules for fasting. “There is no set definition for fasting,” Cooper says.
For example, intermittent fasting may include:
- A single meal each day
- Five days of normal eating and two days restricted to 500 calories
- Overnight fasting between 5 p.m. and 8 a.m.
Because the rules are so fluid, the scientific literature tends to define fasting inconsistently. That makes it “difficult to draw firm conclusions or make recommendations,” Cooper says.
“There are no clear guidelines on how long or how often fasting should occur, or even the best way to fast,” Cooper says.
However, intermittent fasting still might make sense for some people, especially those who are trying to lose weight. “It may be a useful tool for people who find a low-calorie diet difficult to maintain,” Cooper says.
To make sure you fast safely, Cooper suggests incorporating intermittent fasting into a healthy lifestyle and doing so under the supervision of a health care provider.