Time-restricted eating for cardiovascular health: controversy and complexity.
IF, recent headlines are to be believed, time restricted eating (TRE) may not be so good for our hearts, despite many people successfully improving body composition and cardiometabolic markers using this dietary strategy.
Their conclusion pointed to a striking 91% relative increase in CV mortality risk among the TRE group compared to a reference group with a broader eating time window.
But does this study truly shed light on the effects of TRE, or does it rather exemplify the pitfalls, complexity and nuance of nutritional epidemiology?
TRE, a dietary pattern that confines food consumption to a specific eating window during the day, has gained popularity as a straightforward approach to weight management. Unlike diets focusing on calorie counting or specific macronutrient splits, TRE simplifies eating habits by setting a defined timeframe for consumption, often leading to spontaneous caloric reduction and weight loss. Its simplicity and effectiveness have made TRE a subject of numerous studies, aiming to elaborate its implications for health beyond weight loss.
This poster presentation, presented at an American Heart Association conference, is not yet peer-reviewed. It utilised data from the National Health and Nutrition Examination Survey (NHANES), spanning 2003 to 2018, and involving over 20,000 U.S. residents. By analysing food recall questionnaires from these participants, the team sought to investigate the long-term effects of TRE on mortality, particularly cardiovascular death. Their conclusion pointed to a striking 91% relative increase in CV mortality risk among the TRE group compared to a reference group with a broader eating time window.
Association of 8-Hour Time-Restricted Eating with All-Cause and Cause-Specific Mortality. American Heart Association Epidemiology and Prevention|Lifestyle and Cardiometabolic Health Scientific Sessions 2024, Abstract P192
However, closer examination reveals several critical shortcomings:
Firstly, the reliance on self-reported food intake data introduces significant recall bias, potentially skewing the accuracy of the participants’ eating windows. Additionally, the study’s categorisation of participants based on their average eating duration might not adequately represent their habitual dietary patterns over the years as this was determined on the basis of two 24-hour recall questionnaires, extrapolating that to represent their eating behaviour over the following 8-17 year follow-up.
Another point of contention lies in the study’s adjustments for various factors, including lifestyle habits and pre-existing conditions. The TRE group, characterized by a higher average BMI, smoking prevalence, and younger age, differed significantly from the non-TRE group, complicating direct comparisons. Furthermore, the disproportionate number of CV deaths among participants with pre-existing conditions within the TRE group suggests that factors beyond eating duration may contribute to the observed outcomes.
Reverse causality is another potential alternative explanation for the surprising findings; those who developed cardiovascular disease may have other unhealthy lifestyle habits that that contribute to heart disease but that are associated with irregular and erratic eating habits.
Critics argue that the study’s methodology, particularly its retrospective observational design and reliance on self-reported dietary data, limits its ability to establish causal relationships. Nutritional research, fraught with challenges in isolating variables and ensuring long-term adherence to dietary patterns, often struggles with these issues.
Despite these criticisms, the study reignites important discussions on the nuances of nutritional science and the interpretation of epidemiological data. The field’s complexity necessitates cautious analysis and interpretation, especially when translating findings into public health recommendations.
Time-restricted eating continues to show promise as a tool for weight management and possibly other health benefits. However, as with any dietary approach, individual factors such as nutritional needs, lifestyle, and pre-existing health conditions must be considered. Future research, particularly randomised controlled trials with rigorous methodologies, will be crucial in providing clearer insights into TRE’s long-term health implications.
In summary, while the recent study on TRE and cardiovascular mortality raises important questions, it also underscores the challenges in nutritional epidemiology. Sensational headlines and premature conclusions can do more harm than good, misleading the public and oversimplifying the complexities of diet and health, leaving a critical and nuanced analysis indispensable.
