New research presented at an American Heart Association professional conference has linked a popular diet to alarming health dangers. Intermittent fasting remains a popular eating style, but new data suggests long-term adherence to this diet may pose previously unconsidered risks. Is this the beginning of the end for this trendy diet? Here’s what the science says.

What Is Intermittent Fasting?
Intermittent Fasting (IF) as a diet has gained popularity in recent years. According to The International Food Information Council, IF is one of the most popular eating patterns across a wide range of populations. As the name suggests, IF involves cycles of fasting and eating windows of time. There is no one-size-fits-all style to IF and methods and timing vary. Some versions go as far as to limit intake to one meal per day, which is considered too restrictive by medical professionals. IF patterns also lack guidance on what to eat (there are no banished food groups or macronutrient targets), but the format aims to achieve caloric restriction via timing.

Research to date has been limited and mixed on the effects of IF and health. Some studies have linked IF with benefits such as short-term weight loss, improvement in cardiovascular profile, longevity, and diabetes, while other studies have discounted said benefits.

Time Restricted Feeding
One of the most common and popular protocols of IF is Time Restricted Feeding (TRF) which calls for a daily, set timeframe for eating. This is commonly executed “16:8” with 16 hours of fasting and an eight-hour window for eating. This feeding window can be placed at any time of day, with a 12 p.m. to 8 p.m. timeframe often cited. Tightening the timeframe in which people can eat does lend itself to the possibility of caloric restriction, but this can also be achieved over a longer period throughout the day. Long-term considerations of this condensed window could limit nutrient intake and could lead to deficiencies, depending on what IF dieters choose to eat.

The New Data
Just days ago, at the American Heart Association Epidemiology and Prevention|Lifestyle and Cardiometabolic Health Scientific Sessions in Chicago, data was presented in a poster session (but not yet published in a peer-reviewed journal) to indicate that TRF in a 16:8 method was linked to a 91-percent greater risk of cardiovascular death compared to eating in a 12-to-16-hour window of the day. This higher risk of mortality was observed in both the general population as well as those with cardiovascular disease and cancer. The data also determined that eating meals in a window greater than 16 hours was associated with a lower risk of death in patients with cancer.

In this review of over 20,000 adults as part of the National Health and Nutrition Examination Surveys (NHANES), participants were followed for several years – with a median of eight years, up to a maximum of 17 years, which is far longer than most current published studies on IF. There was an even distribution of men and women among the participants; the average age was 49 years. While these findings were based on self-reporting and do not indicate cause-and-effect conclusions, they draw further attention to the need to study IF patterns for extended periods.

Bottom Line: Research on Intermittent Fasting and its impact on health is ongoing and more studies are needed on the long-term effects of eating all your food in an eight-hour window of the day.