What are the effects of intermittent fasting on heart health? The study presented at an American Heart Association conference suggests a potential association between time-restricted eating and an increased risk of cardiovascular disease-related death.
However, it’s crucial to understand that this is an observational study, meaning it doesn’t establish a cause-and-effect relationship between time-restricted eating and cardiovascular death but rather identifies an association.
Several factors should be considered before drawing definitive conclusions from the study. For instance, the types of foods consumed by participants were not detailed in the preliminary findings, as the analysis has yet to undergo peer review for publication in a medical journal.
From a nutrition science perspective, focusing solely on when foods are consumed, as in time-restricted eating, may overlook the importance of food quality.
Quality nutritional choices, regardless of the timing of consumption, are essential for overall health and well-being. Therefore, more comprehensive research is needed to fully understand the potential impacts of time-restricted eating on health outcomes.
Earlier Research: Time-Restricted Eating’s Impact on Short-Term Heart Health
Earlier research has indicated that time-restricted eating, where individuals consume calories within a specific window of hours each day, can lead to improvements in various measures of heart health in the short term.
This eating pattern typically involves fasting for a certain number of hours, followed by a designated period for calorie intake, such as the popular 16:8 schedule, where fasting lasts for 16 hours and eating occurs within an eight-hour window.
Studies, which have mainly focused on short-term follow-ups ranging from one month to one year, have shown that time-restricted eating can positively impact several cardiometabolic health markers. These improvements include reductions in blood pressure, blood glucose levels, cholesterol levels, and the prevalence of overweight or obesity.
New Risks Related to Time-Restricted Eating Unveiled in New Study
The new study utilized data collected over several years, with a median follow-up period of eight years and a maximum of 17 years. The information was gathered from approximately 20,000 U.S. adults participating in the annual 2003–2018 National Health and Nutrition Examination Surveys.
Upon enrollment, participants completed two questionnaires recalling their dietary intake over the previous 24 hours. Based on the length of their eating window, individuals were categorized into one of five groups, ranging from less than 8 hours to 16 hours.
Researchers then tracked the health outcomes of the subjects over the years. After adjusting for various factors including age, race, ethnicity, and history of disease, the study found that:
Individuals who restricted their eating window to less than eight hours per day had a 91 percent higher risk of death from cardiovascular disease (primarily heart disease and stroke) compared to those with a window of 12 to 16 hours.
Among participants with pre-existing heart disease, having an eating window of 8 to 10 hours per day was associated with a 66 percent higher risk of death from cardiovascular disease.
However, time-restricted eating did not appear to reduce the overall risk of death from any cause.
Limitations of The New Study
Nutrition experts commenting on the new research have highlighted limitations in the study setup that may raise questions about the findings.
They argue that the conclusions drawn from the study may be overstated due to the fact that the investigators only had data on dietary intake for two days over a 20-year period. They questioned what the subjects were eating on the other 7,300 days of the study. While it’s an improvement over just one day of data, relying on only two days may lead to the misclassification of many participants.
Experts suggest that a better approach would have been to collect dietary data from multiple days in the first year, followed by additional data from subsequent years. This would provide a more comprehensive understanding of participants’ eating habits over time.
The study’s lead author acknowledges this limitation but notes that the analysis excluded individuals who reported an atypical diet on either of the two days, which may have helped mitigate some of the misclassification issues.
Stress Levels and Access to Food May Impact the Results of the Study
Several factors could have influenced the risk of heart disease among the study participants, although these factors may be addressed once the full analysis is published.
For instance, it’s possible that individuals with shorter eating windows had less access to food, worked more shifts, and experienced higher levels of stress compared to those in the 12 to 16-hour category. If this were the case, the observed associations with cardiovascular deaths might be attributed to factors other than the duration of the eating window.
Further Research is Necessary
Researchers agree that more studies on time-restricted eating are needed before specific recommendations can be made based solely on the findings of this study. However, they suggest approaching long-term adherence to this eating pattern with caution.
Instead of solely advocating for time-restricted eating, researchers recommend focusing on diets with established health benefits, such as the DASH diet and Mediterranean diet. Current evidence suggests that the quality of food consumed may be more crucial than the timing of meals. Nevertheless, time-restricted eating may offer psychological benefits for some individuals.
It’s noted that many individuals struggle to make healthy choices in the current food environment, where low-quality foods are readily available, affordable, and appealing. Despite this, some individuals may find a time-restricted diet beneficial from a behavioral psychology standpoint.