Intermittent fasting has gained popularity lately as a dietary approach with potential health advantages. So you may have been surprised to see headlines last week suggesting the practice could increase an individual’s risk of death from heart disease.
The news stories were based on recent research which found a link between time-restricted eating, a type of intermittent fasting, and an increased risk of death from heart problems, or heart disease.
So what can we make of those findings? And how do they measure up with what else we find out about intermittent fasting and heart disease?
The study in query
The research was presented as a scientific poster at an American Heart Association conference last week. The full study hasn’t yet been published in a peer-reviewed journal.
The researchers used data from the National Health and Nutrition Examination Survey (NHANES), a long-running survey that collects information from a lot of people within the United States.
This form of research, referred to as observational research, involves analysing large groups of individuals to discover relationships between lifestyle aspects and disease. The study covered a 15-year period.
It showed individuals who ate their meals inside an eight-hour window faced a 91% increased risk of dying from heart disease in comparison with those spreading their meals over 12 to 16 hours. When we glance more closely at the information, it suggests 7.5% of those that ate inside eight hours died from heart disease through the study, in comparison with 3.6% of those that ate across 12 to 16 hours.
We don’t know if the authors controlled for other aspects that may influence health, equivalent to body weight, medication use or weight-reduction plan quality. It’s likely a few of these questions can be answered once the total details of the study are published.
It’s also value noting that participants could have eaten during a shorter window for a variety of reasons – not necessarily because they were intentionally following a time-restricted weight-reduction plan. For example, they could have had a poor appetite as a result of illness, which could have also influenced the outcomes.
Other research
Although this research could have quite a lot of limitations, its findings aren’t entirely unique. They align with several other published studies using the NHANES data set.
For example, one study showed eating over an extended time frame reduced the chance of death from heart disease by 64% in individuals with heart failure.
Another study in individuals with diabetes showed those that ate more steadily had a lower risk of death from heart disease.
A recent study found an overnight fast shorter than ten hours and longer than 14 hours increased the chance dying from of heart disease. This suggests too short a quick may be an issue.
But I assumed intermittent fasting was healthy?
There are conflicting results about intermittent fasting within the scientific literature, partly as a result of the different sorts of intermittent fasting.
There’s time restricted eating, which limits eating to a time frame every day, and which the present study looks at. There are also different patterns of fast and feed days, equivalent to the well-known 5:2 weight-reduction planwhere on fast days people generally eat about 25% of their energy needs, while on feed days there is no such thing as a restriction on food intake.
Despite these different fasting patterns, systematic reviews of randomised controlled trials (RCTs) consistently show advantages for intermittent fasting by way of weight reduction and heart disease risk aspects (for instance, blood pressure and levels of cholesterol).
RCTs indicate intermittent fasting yields comparable improvements in these areas to other dietary interventions, equivalent to every day moderate energy restriction.
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So why will we see such different results?
RCTs directly compare two conditions, equivalent to intermittent fasting versus every day energy restriction, and control for a variety of things that would affect outcomes. So they provide insights into causal relationships we are able to’t get through observational studies alone.
However, they often deal with specific groups and short-term outcomes. On average, these studies follow participants for around 12 months, leaving long-term effects unknown.
While observational research provides precious insights into population-level trends over longer periods, it relies on self-reporting and can’t show cause and effect.
Relying on people to accurately report their very own eating habits is difficult, as they could have difficulty remembering what and once they ate. This is a long-standing issue in observational studies and makes relying only on a lot of these studies to assist us understand the connection between weight-reduction plan and disease difficult.
It’s likely the connection between eating timing and health is more complex than simply eating roughly recurrently. Our bodies are controlled by a bunch of internal clocks (our circadian rhythm), and when our behaviour doesn’t align with these clocks, equivalent to once we eat at unusual times, our bodies can have trouble managing this.
So, is intermittent fasting protected?
There’s no easy answer to this query. RCTs have shown it appears a protected option for weight reduction within the short term.
However, people within the NHANES dataset who eat inside a limited period of the day seem like at higher risk of dying from heart disease. Of course, many other aspects might be causing them to eat in this manner, and influence the outcomes.
When faced with conflicting data, it’s generally agreed amongst scientists that RCTs provide the next level of evidence. There are too many unknowns to simply accept the conclusions of an epidemiological study like this one without asking questions. Unsurprisingly, it has been subject to criticism.
That said, to realize a greater understanding of the long-term safety of intermittent fasting, we want to have the option follow up individuals in these RCTs over five or ten years.
In the meantime, when you’re eager about trying intermittent fasting, you need to speak to a health skilled first.