Intermittent fasting has been the darling of the wellness world for years, with promises of weight loss, better blood sugar, and even a longer life.
But a new study has thrown a spanner in the works, revealing that one of the most popular fasting methods—the eight-hour eating window—could put your heart at serious risk.
At the 2024 American Heart Association conference, researchers presented data from a study involving more than 20,000 American adults. The research suggests it may raise your risk of dying from heart disease by a staggering 91 per cent.
The findings were eye-opening: people who limited their eating to just eight hours a day had nearly double the risk of dying from cardiovascular disease compared to those who spread their meals over 12 to 16 hours.
The lead researcher, Dr Victor Zhong, stressed that these weren’t just numbers on a page.
The study followed real people over time, tracking their health outcomes. While the research is observational (meaning it can’t prove cause and effect), its sheer size and scope have made experts sit up and take notice.
Animal studies have long suggested that intermittent fasting could benefit the heart. Mice on time-restricted diets showed better heart function and metabolism.
But humans aren’t mice, and our bodies may not respond the same way to extreme eating patterns.
New research suggests that compressing all meals into a short window could have unintended consequences, especially for older adults and those with heart issues.
What’s going on inside the body?
Let’s break down some of the possible reasons why an eight-hour eating window might be risky:
1. Muscle loss—a hidden danger for over-50s
When you fast for long periods, your body doesn’t just burn fat—it can also break down muscle for energy.
For those of us over 50, this is a big deal. Age-related muscle loss (sarcopenia) is already a concern, and losing more muscle can weaken your heart and make you more vulnerable to illness and injury.
2. ‘Reward eating’ and poor food choices
Another issue is what happens during those eight hours. Many people eat larger, richer meals, often high in fat and sugar.
This can raise your LDL (‘bad’) cholesterol and increase TMAO (trimethylamine N-oxide) levels, a compound linked to clogged arteries.
3. Disrupted body clocks
Eating late at night to fit your meals into a short window can throw off your circadian rhythm—your body’s natural clock.
This disruption has been linked to higher blood pressure, poor sleep, and metabolic problems, all of which can strain your heart.
Who should be most concerned?
The risks aren’t the same for everyone. The study found that people over 65 and those with existing heart conditions are especially vulnerable.
If you’re already managing high blood pressure, high cholesterol, or have a family history of heart disease, it’s worth thinking twice before jumping on the eight-hour fasting bandwagon.
Is all intermittent fasting dangerous? Not necessarily. The study found that people who ate within a 12-hour window didn’t have the same increased risk.
A 12- to 16-hour eating window may be much safer, mainly if you focus on healthy, balanced meals.
This new research doesn’t mean you need to abandon intermittent fasting altogether. But it does mean that one-size-fits-all advice is out the window.
What works for a 30-year-old gym junkie may not be right for someone in their 60s with a heart condition.
As with all things health-related, it’s about finding what works for you—and being willing to adjust as new evidence comes to light.
Have you tried intermittent fasting? Did you notice any changes in your health, good or bad? Are you rethinking your approach after reading about this new research? Share your experiences and questions in the comments below.
Disclaimer: The information in this article is for general informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Everyone’s health is unique, so it’s always best to consult a qualified healthcare professional if you have any concerns or questions about your health. We encourage you to seek expert guidance before making any medical decisions.
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