A March 2024 study linked intermittent fasting to 91% higher heart death risk, sparking panic. But the observational design, two-day self-reporting, and missing health data mean the headline tells a very incomplete story.
What the Study Actually Found
This was an observational study, meaning researchers watched patterns unfold without testing whether fasting causes heart problems. The study shows association, not causation. Participants self-reported their eating times through just two days of 24-hour dietary recalls. Those two snapshots were then used to categorize years of eating behavior. Anyone who has ever had an unusual eating day can see the problem. Two days is a narrow window to define someone’s long-term habits. Observational designs also cannot fully account for confounding variables like exercise, stress management, or medications. These factors shape heart health profoundly, and they were not controlled in the way a randomized trial would require.
The Missing Context Everyone Overlooked
Perhaps the most significant gap involves who was eating in those restricted windows and why. Some participants may have been eating less because they were already sick. People battling chronic illness, depression, or advanced disease often lose appetite and eat during shorter periods. This creates what researchers call reverse causation: the restricted eating did not cause poor health outcomes; poor health caused the restricted eating. The study also did not distinguish between someone intentionally practicing intermittent fasting with nutrient-dense meals and someone skipping meals due to poverty, food insecurity, or chaotic work schedules. These are vastly different scenarios with vastly different health implications. And critically, no data captured what people ate during their windows. An 8-hour eating period filled with processed food tells a completely different metabolic story than one built around whole foods, healthy fats, and lean protein.
