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Is intermittent fasting really risky?

Barbara Philipps - 26/03/2024 - 0 comments


Is intermittent fasting linked to a higher risk of cardiovascular death?

Scientists at the American Heart Association’s scientific sessions presented a poster with data claiming that intermittent fasting is linked to higher risks of cardiovascular death (Source). The information was picked up by major international news websites including the Washington Post, NBC, Skynews, and went viral.

However, the news should be regarded with scepticism. The analysis has not yet been peer-reviewed or published in an academic journal. It was presented as a poster in a conference setting format where there is no examination of the validity of the findings. The results are from a large epidemiological study, and this is typically the kind of research that does not infer causality.

This is not the first time that data from this cohort has been criticised. There has been some discussion about the validity of studies which suggest that skipping breakfast increases the risk of cardiovascular diseases in the U.S. Similar epidemiological studies, including some that use the same data as this new study, have numerous biases, as explained by Peter Attia (as Peter Attia explains). Definitions of skipping breakfast are heterogenous and it is difficult to separate the chaff from the wheat. In the U.S., adults who skip breakfast more often are less health-conscious than those who skip breakfast less often. It is possible that nighttime eating and other unhealthy habits, and not skipping breakfast per se, is responsible for the effect on chronic disease.

Scientists around the world have expressed doubts about the validity of these results. As highlighted by Pam R. Taub, Cardiologist and Professor of Medicine at UC San Diego, there were 31 cardiovascular incidents among 414 participants in the cohort who abstained from eating over eight hours during an average eight-year monitoring period. This subset accounted for merely 2% of the entire cohort (414 out of 20,078 individuals). Notably, there was a 60% higher prevalence of smokers within this group (23.2% compared to 6.6% in the control group).

By contrast, numerous studies show that fasting can normalise risk factors for cardiovascular diseases. This is the case for intermittent fasting, and even for long-term fasting as shown in our own studies. It is therefore likely that intermittent fasting per se is not linked to a higher risk of cardiovascular death.

In general, there is no conclusive evidence regarding the optimal eating window. Neither was this studied in detail by the authors of the study in question. Time-restricted eating can mean skipping either breakfast or dinner. Comparisons between restricting food intake early and late in the day reveal that skipping dinner or eating it early is linked to more health benefits than skipping breakfast. Learn more!

The ideal time window for food intake

The ideal eating window basically depends on our inherent biological design: Nighttime is meant for resting and fasting to promote cell and tissue rejuvenation. The duration of a fast should be tailored to factors like age, weight, and health status. Cardiovascular issues are influenced not by fasting intervals, but by dietary choices and physical activity, among other factors.