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  • Writer's pictureDr. Cari S. Miller

Does Intermittent Fasting/Time-Restricted Eating Increase the Risk of Cardiovascular Death?

I’m sure you have seen the most recent news article headlines beamed across the internet, news outlets, and social media platforms “8-hour time-restricted eating linked to a 91% higher risk of cardiovascular death” followed with shocking amounts of exclamation points for added effect. Unfortunately, this type of sensationalism is a common occurrence: the new media is presenting the latest “thing” to keep you scared, afraid, and confused. So, what is all the hype about and should you care?

AHA: Don't Fast - Eat these Instead


On March 18, 2024, Researchers presented data from a retrospective observational study at a poster session wherein they deduced from the study data that time-restricted eating was associated with a 91% increase in cardiovascular DEATH.  Moreover, seemingly to provide credibility to the poster /study findings were presented by the American Heart Association: American Heart Association Epidemiology and Prevention|Lifestyle and Cardiometabolic Health Scientific Sessions 2024, Abstract P192. However, when you actually look at the study (which few people do – most just take the interpretation from news sources), you will find the results are virtually meaningless.


This study data was presented at poster session, which means the study details are very limited and the full study results still need to be peer-reviewed prior to anything being actually published. In reading through the actual study, you will find the goal of the study was to determine how long-term time-restricted eating affected mortality, something which would be very difficult to do even in a randomized control trial, the type of study which could provide the most robust and highest levels of evidence. Instead, researchers conducted a retrospective (meaning backwards looking) observational study using SELF_REPORTED DATA (meaning the participants provide the information without any validation) from ~20K people in the National Health and Nutrition Examination Study (NHANES) collected between 2003-8. The NHANES looks at demographic, biomarker, and dietary data from ~5K randomly selected people from across the United States to track changes in population trends. This study asks each participant to recall what they ate, how much, at what times on the previous day. The study required every participant to complete two food recall surveys less than two weeks apart, and then averaged their feeding windows to determine that participants' eating duration.  


Just think about this for a moment and do it yourself. Try to quantify exactly how much food you ate yesterday and recall exactly what time it was when you ate it. What are the chances you could do this with accuracy and relate it into a survey. Furthermore, when conducting these types of observational studies with self-reported data we have to recognize there is a high margin of error, as well as potential for dishonesty – whether on purpose or not. Obviously, with a large group of participants, the data becomes corrupted with many different types of recall biases. This matters significantly, especially for this particular study because if the participants “misremembered” or “misrepresented” the time of their food intake, their eating duration would change. And this matters, because this is THE foundational focus of this study.


Using the data collected, the researchers then calculated eating patterns and examined the participants health outcomes over an average of 8 years. They looked at the participants mortality (death) data: all cause mortality, cardiovascular mortality, and cancer mortality using the National Death Index Database. The data was adjusted using a very high number of variables: age, sex, race, total energy intake, education, income, food security status, smoking, drinking, physical activity, diet quality score, body mass index, body mass index squared, and other self-reported health conditions. Just looking at those adjustments should give any critical thinker pause and question the study’s validity. Just think about all of the adjustments and how they may impact dietary patterns or health patterns and how these may then confound the findings related to feeding windows and mortality.


The findings of the study were statistically examined and based on a single factor – feeding window. It was determined from the data, the 8-hour time-restricted eating group was found to have a hazard ratio for cardiovascular death of 1.91 (95% CI: 1.20-3.03) compared to the reference group, with a 12-16 hour feeding window. This presented a RELATIVE 91% increase in the risk of cardiovascular death. That – and only that – is what is driving the headlines. Not the other differences found, which are important to make sense of the data, such as the significant differences in other lifestyle habits and co-morbidities, meaning the relative increase in cardiovascular deaths was disproportionately driven by the deaths of people with pre-existing conditions – which obviously contribute to multiple drivers of WHY people may have incorporated time-restricted eating in the first place, such as already having a disease state they are trying to address, specifically things like diabetes. The total sample size which the researchers derived this shocking information from was limited to 414 participants in the time-restricted eating group, with 31 deaths, and the reference group of 11,831 participants with 423 deaths. Additionally, the time-restricted eating group had a higher average BMI, higher % smokers, and were younger – indicating these groups are very different in more than just their eating duration, which makes it impossible to compare the two groups.


Lastly, the researchers concluded their poster presentation the following statement: “Although the study identified an association between an 8-hour eating window and cardiovascular health, this DOES NOT MEAN THAT TIME-RESTRICTED EATING CAUSED CARDIOVASCULAR DEATH.” Please, read that statement again.


The bottom line of this study, and the media frenzy which followed, is the information is being sensationally presented with an OBVIOUS bias intended to scare people away from time-restricted eating, which has numerous demonstrated health benefits. It made headlines because of its association to the American Heart Association. However, most people do not realize the American Heart Association is SPONSORED by the food industry: American Heart Association Forum Members, as well as the pharmaceutical industry: Pharmaceutical Ties to American Heart Association. DO NOT BE AFRAID to incorporate time-restricted or intermittent fasting into your dietary practices. We can all benefit from incorporating intermittent fasting into our health regimen. Don’t get caught up accepting everything the news media flashes before your eyes. Stop and ask yourself, who benefits from these types of sensational and fear inducing studies and articles? Is it the billion-dollar food industry or the billion-dollar pharmaceutical industry. Chances are it is one of the two.


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