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You may have seen the headlines: “Intermittent fasting linked to 91 percent increase in risk of death from heart disease”; “The intermittent fasting trend may pose risks to your heart.”
The news came from an abstract presented Monday at an American Heart Association conference in Chicago. The study has not yet been published in a peer-reviewed journal, and experts cautioned that it had many limitations. Here’s what we know.
The Background
Intermittent fasting involves cycling between eating and fasting for specific periods of time. A common approach, for example, is to eat only within an eight-hour window each day, said Krista Varady, a professor of nutrition at the University of Illinois Chicago.
Several short-term trials have suggested that this eating style can lead to some weight loss and may lower blood pressure and improve blood sugar control in certain people, she said.
But the longest intermittent fasting trial lasted only one year, said Victor Wenze Zhong, lead author of the new study and an epidemiologist at Shanghai Jiao Tong University School of Medicine in China. His aim, he said, was to look at longer term health.
The Research
The new study included more than 20,000 adults from the United States. The participants completed two questionnaires, less than two weeks apart, about what time they ate on the previous day. The researchers then calculated the participants’ average eating windows and assumed it was their typical schedule for the rest of the study, Dr. Zhong said. The participants were followed for an average of eight years.
During that time, the participants who limited their eating to eight hours in a day had a 91 percent greater chance of dying from cardiovascular disease than those who ate over a 12- to 16-hour time frame, the researchers reported.
But there were just 414 people in the eight-hour eating group, Dr. Zhong said. And they tended to be younger; less educated and wealthy; have less access to food; and be more likely to smoke than the other participants.
The researchers accounted for these factors in their analysis, Dr. Zhong said. But the study did not show that this style of eating caused deaths from cardiovascular disease, only that the two were linked.