Is it true that following a fasting diet some of the time can lower my risk of heart disease?

Answer From Donald Hensrud, M.D.

Maybe. Fasting means not eating or drinking for a certain amount of time. Some types of fasting may improve some risk factors linked to heart health. But researchers aren’t sure why.

Intermittent fasting is a pattern of eating of meals during a set period. Intermittent fasting methods include:

  • Alternate-day fasting. You eat as usual on one day. Then you fast or eat little the next day.
  • 5:2 fasting. You eat as usual five days a week. Then you cut calories way down two days a week.
  • Time-restricted eating. You eat only between certain hours of the day, such as between 11 a.m. and 7 p.m., or noon and 6 p.m.

Research results on intermittent fasting are mixed. Short-term studies suggest there is greater weight loss with intermittent fasting than with regular calorie cutting. But longer studies from six months to one year have not all found this to be true.

Some studies say that intermittent fasting may lower low-density lipoprotein (LDL) cholesterol, the “bad” cholesterol. Intermittent fasting also may improve the body’s response to a hormone called insulin. Insulin helps control blood sugar levels. Higher LDL cholesterol and higher blood sugar levels in diabetes are risk factors for heart disease.

But a recent study suggested that restricting eating times to fewer than eight hours a day may be linked to a higher risk of dying of heart disease. And a review of studies on intermittent fasting found that the weight and blood sugar changes reported were small. More research is needed to see whether regular fasting can reduce the risk of heart disease.

The side effects of intermittent fasting aren’t well known. Some people have headaches, mood swings and dizziness. More study is needed to know the long-term effects.

Intermittent fasting isn’t for those who:

  • Have an eating disorder.
  • Are pregnant or breastfeeding.
  • Take medicine for diabetes.
  • Have a history of low blood sugar, called hypoglycemia.

If you’re thinking about intermittent fasting, talk to your healthcare professional about the pluses and minuses. Remember that a heart-healthy diet and regular exercise can improve heart health.