Can intermittent fasting improve heart health?

Fasting — or purposely not eating food — dates back to ancient times when people fasted in hopes of curing a disease or for religious reasons. Today, different forms of fasting remain popular for their possible health benefits, including weight loss and improvements in heart-related risks. A recent review article suggests some potential benefits (see "Intermittent fasting: The latest evidence"). But timing isn't everything — you still need to pay attention to the overall quality and quantity of the food you eat.

Intermittent fasting includes a range of strategies to limit the timing and frequency of meals. One variation, time-restricted eating, involves eating only during a certain time window (usually eight hours) over a single day. For example, you would have food only during the hours of 9 a.m. to 5 p.m. and then eat nothing during the other 16 hours.

Another approach, alternate-day fasting, involves fasting or significantly limiting calories for a full day. You choose certain days during the week when you eat nothing or limit yourself to just 400 to 600 calories per day. On the other days of the week, you follow your normal eating pattern. In one popular version, the 5:2 diet, you eat normally on five days, but restrict your calories on two nonconsecutive days. With alternate-day fasting, you eat a calorie-restricted diet every other day.

Pros and cons for fasting

"Generally speaking, intermittent fasting has a good safety profile," says Dr. Armen Yerevanian, an endocrinologist at Harvard-affiliated Massachusetts General Hospital. People with diabetes who rely on insulin and certain medications to lower their blood sugar levels need to be cautious, however. For them, fasting isn't dangerous, but it requires careful planning with their doctor to minimize the risk of low blood sugar.

Intermittent fasting probably helps improve cholesterol levels and other heart risk factors because the practice promotes weight loss. Because of the time restrictions, you naturally tend to eat fewer calories, especially if you shut down a habit of late-night binge eating. Plus, when you don't eat for extended periods of time, your body switches fuels away from carbohydrates and starts burning stored fat.

Challenging to maintain

"The biggest issue with intermittent fasting is that it can be challenging to maintain over the long run," says Dr. Yerevanian. Most studies of the practice have lasted just 12 to 16 weeks, although some have gone up to six months. It's easier to stick to a diet when you're being closely watched as part of a study, he says. But in the real world, it's often hard to follow a strict eating schedule when you're also juggling various work, family, and social commitments.

"The times that I've seen time-restricted eating be most successful is when people are ready to make a broad set of lifestyle changes to improve their health," says Dr. Yerevanian. Rather than relying solely on intermittent fasting, they use it as a tool to change other aspects of their lifestyle that are affecting their weight and heart risks. Combined with a healthy, plant-focused diet, along with regular aerobic and strength-building exercise and routine preventive care, intermittent fasting can be a safe and effective tool to improve your cardiovascular health.

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