Eating in an 8-Hour Window May Raise Heart Risk by 135%, Study Finds
Eating in an 8-Hour Window May Raise Heart Risk by 135%, Study Finds
Long-term data from over 19,000 adults links extreme intermittent fasting to higher cardiovascular mortality
Intermittent fasting has been widely embraced as a health trend, with tech leaders, celebrities and fitness enthusiasts swearing by its benefits. But a new long-term study suggests that eating within an extreme eight-hour window each day may significantly raise the risk of cardiovascular death.
Published in Diabetes & Metabolic Syndrome: Clinical Research and Reviews and reported in ScienceDirect, the study analysed dietary patterns of more than 19,000 U.S. adults from the National Health and Nutrition Examination Survey (NHANES) between 2003 and 2018. Over a median follow-up of eight years, researchers found that individuals who limited eating to under eight hours daily faced a 135% higher risk of cardiovascular mortality compared with those who ate over a 12–14-hour window.
The elevated risk was consistent across age, sex, race, socioeconomic status and lifestyle factors. It was especially pronounced among smokers, diabetics and people with pre-existing heart disease.
Professor Victor Wenze Zhong of Shanghai Jiao Tong University School of Medicine, who led the research, said that while short-term trials hinted at heart health benefits, this extended dataset paints a different picture. He stressed the importance of personalised dietary guidance instead of one-size-fits-all fasting plans.
Doctors caution, however, that the study was observational, meaning it shows associations rather than proving causation. Neurologist, from Hyderabad noted that factors like existing illness or underreporting of diets could also play a role, as people who are already unwell may naturally eat less.
Still, multiple sensitivity analyses confirmed the robust link between extreme fasting windows and cardiovascular deaths. The study found no clear association with overall mortality or cancer-related deaths.
Experts point out that intermittent fasting can still offer benefits such as weight loss, improved insulin sensitivity, lower blood pressure and reduced inflammation. But they warn that drawbacks nutrient deficiencies, irritability, and added risks for older adults or those with chronic illnesses, should not be overlooked.
Moderation, researchers suggest, may be key. A 10–12-hour eating window could balance fasting’s potential benefits with lower health risks. For now, experts recommend focusing more on what people eat rather than rigidly restricting when they eat.
