Practiced and popularised for its proposed weight loss and cardio-metabolic benefits, the 16:8 method of fasting has recently come under scrutiny based on a new study.
Led by senior study author Victor Wenze Zhong in China, the study looked at the eating patterns of 20,000 US adults in relation to causes of death between 2003 and 2019. Data on eating habits was extracted from the National Health and Nutrition Examination Surveys, and mortality reports from the Centers for Disease Control and Prevention’s National Death Index database. Shockingly, the analysis found that people who restricted all their eating to <8 hours of the day were 91% more likely to die from heart disease, compared to those with a more typical 12-16 hour eating window.
Previous research on intermittent fasting has produced mixed results, with some studies supporting a cardio-protective effect and others demonstrating no additional benefit compared to traditional calorie restriction.
Zhong’s findings directly oppose the previously perceived benefits of fasting, and it’s important to note there are several strong limitations to this study.
- Dietary data was drawn from surveys which rely on self-report. This method of data collection is very susceptible to bias i.e. participants may not accurately recall the information and are more likely to report perceived desirable eating habits versus ‘unhealthy’ behaviours.
- Categorisation into the different eating windows was based on only 2 days of reported intake for each participant. Given that participants were followed for an average of 8 years, it’s very unlikely that the 2 days of dietary report were reflective of habitual eating habits over this time.
- Perhaps the biggest limitation of all is that other dietary and lifestyle factors that play a role in health and mortality were not assessed. Nutritional quality of the diet, as well as behaviours such as smoking, exercise, and alcohol consumption are all major variables that are well known to influence health outcomes.
Clearly more research is needed to reach strong conclusions about the benefits or potential harms of fasting. For those interested in trying intermittent fasting, it may be helpful to focus on trying to eat earlier in the evening and stopping other foods and snacks after dinner rather than enforcing a strict ‘fasting’ period. You should always seek the advice of your Dietitian before drastically altering your eating habits.
Reference:
8-hour time-restricted eating linked to a 91% higher risk of cardiovascular death, American Heart Association Epidemiology and Prevention|Lifestyle and Cardiometabolic Health Scientific Sessions 2024, Abstract P192
