Study questions the safety of intermittent fasting
Higher death risk from heart disease is implicated, so consult a doctor before changing eating habits
Intermittent fasting has been touted as a strategy for losing weight, reducing inflammation, improving blood sugar, controlling appetite and more. Now researchers have found that following an eight-hour, time-restricted eating schedule appears to be associated with a significant increase in risk of death from cardiovascular disease.
What does this mean for people who use or may be considering time-restricted eating?
Intermittent fasting involves restricting the hours of eating during the day, usually to a window of between four and 12 hours within 24 hours. The popular 16:8 intermittent fasting eating schedule includes an eight-hour eating period and a 16-hour fasting period. Will Cole’s “Intuitive Fasting,” promoted by actress Gwyneth Paltrow, and many other books on time-restricted eating discuss the strategies, science and potential benefits of fasting. Previous studies have found time-restricted eating to improve indicators of cardiometabolic health including blood glucose, insulin, cholesterol and blood pressure.
Just last month, preliminary study findings presented at American Heart Association scientific meetings revealed a 91% higher risk of death from cardiovascular disease in over 20,000 adults following an eight-hour time-restricted eating schedule. People with heart disease or cancer experienced a greater risk of death from cardiovascular disease as well. Plus, compared with a regular eating pattern during 12 to 16 hours per day, restricting eating to less than eight hours was not associated with longer life.
Research participants were followed over about eight years, with a maximum study period of 17 years. This is a much larger and longer study than previous intermittent fasting studies. However, it’s important to note that there could be variations in diet quality and nutrient density that were not considered in this stage of the research. Also, participants were grouped into different windows of timerestricted eating based on just two days of dietary intake records. Researchers need to better understand how demographic and baseline factors, such as weight, stress levels and cardiometabolic risk factors, of those in the different time-restricted eating windows compare.
Because studies like this cannot account for unknown variables, they can only provide strong evidence of association, not actual cause between factors.
This means the findings don’t prove that time-restricted eating causes more deaths from cardiovascular disease, but that there appears to be a relationship between time-restricted eating and increased death from cardiovascular disease. Either way, the results are both surprising and concerning.
Based on these findings, it’s important to speak with your health care provider before starting time-restricted eating. Those with a history of cancer or cardiovascular disease may not be reasonable candidates for short-term or long-term intermittent fasting.
While intermittent fasting may offer shorter-term health and wellness perks, this new research suggests it may be linked to longer-term adverse health risks. A deeper investigation is needed to better understand the relationship among time-restricted eating, diet quality, adverse health risk and other factors.
LeeAnn Weintraub is a registered dietitian providing nutrition counseling and consulting to individuals, families and organizations. She can be reached at RD@ halfacup.com.