Study Finds Prolonged Intermittent Fasting May Double Risk of Heart Disease Death

A recent study published in the journal Diabetes and Metabolic Syndrome has sparked concern among medical professionals and the public alike, revealing that adults who restrict their daily eating window to less than eight hours—popularly known as “16-hour intermittent fasting”—may face more than double the risk of dying from cardiovascular disease compared to those who eat across a broader time frame. The findings, from an analysis of over 19,000 U.S. adults using NHANES data, highlight new questions about the safety of time-restricted diets, particularly for individuals already at risk for heart disease.

Key Findings

The study’s results indicate a 135% higher risk of cardiovascular mortality among those practicing a daily 16-hour fast (i.e., eating only within an eight-hour window), compared to participants who ate over a 12-14-hour window. This association persisted across diverse subgroups, including different races, ethnicities, and socioeconomic backgrounds.

• No significant links were found between 16-hour intermittent fasting and cancer or all-cause mortality. The increased risk appears to be specific to heart and blood vessel diseases such as heart attacks and strokes.

• These conclusions build upon earlier research: a retrospective study presented at the American Heart Association conference in March 2024 echoed similar findings, reporting a 91% increased risk of heart disease death in those who regularly fast for 16 hours daily.

Expert Commentary

“Although [confounding factors exist], people should be extremely cautious about adopting a short eating window long-term to pursue cardiovascular health or longevity, which has no evidence support from human studies to date,” said Victor Wenze Zhong, senior author of the flagship NHANES study.

Prominent Indian cardiologist Dr. Ranjan Shetty of Sparsh Hospital, Bengaluru, shared that randomized trials are needed to confirm these findings, as existing studies may not fully account for participants’ baseline health, weight, or underlying risk factors. He added that “severely restricting calories can lower blood sugar, trigger heart palpitations, and elevate heart rate, potentially leading to heart attacks—especially for those with arrhythmia, diabetes, or existing cardiac conditions.”

Dr. Anoop Misra, Chairman of Endocrinology at Fortis C-DOC, cautioned:

“Intermittent fasting is a promising tool in our dietary arsenal—low cost and simple—but enthusiasm should be tempered with careful risk assessment. Until more long-term data are available, intermittent fasting should be individualized, ideally supervised for those with pre-existing conditions, and applied only for short-term periods.”

Context and Background

Intermittent fasting (IF), especially the 16:8 model, has been popularized for its potential benefits: weight loss, improved insulin sensitivity, lower blood pressure, reduced inflammation, and better lipid control. Many adopt IF hoping to safeguard against chronic illness or promote longevity.

However, mounting evidence suggests that extreme or poorly managed fasting regimens can lead to nutrient deficiencies, excessive hunger, irritability, headaches, and reduced adherence over time. There remains substantial variability in results depending on individual health status, dietary choices within the eating window, and the duration of fasting periods.

Notably, randomized controlled trials have yet to definitively prove that IF prevents cardiovascular events or improves survival. Some research even highlights possible short-term increases in mortality risk associated with fasting, attributed to physiological stress and metabolic disruptions.

Implications for Public Health

For general readers and health professionals:

• Personalized Nutrition Is Critical: Experts consistently recommend that dietary strategies—especially restrictive plans like IF—should be tailored to individual health status and goals, not adopted universally.

• Medical Supervision Advised: Those with chronic illness (e.g., heart, kidney, liver disease, diabetes), elderly individuals, children, and people with eating disorders should avoid restrictive fasting without physician guidance.

• Food Choices Matter: The cardiovascular risk connected to IF may be exacerbated by unhealthy food selections, such as high fat, sugar, and sodium intake—even within a narrow eating window.

• Monitor for Adverse Effects: Signs of hypoglycemia, abnormal heart rhythms, or muscle loss should prompt reevaluation of fasting routines.

The current study does not dispute that IF may offer weight loss or metabolic benefits, but it urges caution and calls for longer and more rigorous research, focusing on cardiovascular outcomes and identifying subgroups for whom such plans may be unsafe.

Counterarguments and Limitations

• Observational Nature: The cited studies are predominantly observational and retrospective. Without randomized trials, confounding factors—including existing disease, medication use, and lifestyle habits—could skew results.

• Self-Reported Data Risks: Reliance on self-reported eating patterns introduces potential errors, such as inaccurate recall or underreporting.

• Heterogeneity in Fasting Protocols: Variability in fasting durations, food quality, and overall caloric intake complicates direct comparisons across studies.

Some clinical trials, such as INTERFAST-MI, even report improvements in cardiac function and metabolic markers associated with IF, underscoring that context and individual factors remain crucial.

Practical Tips for Readers

• Consult healthcare providers before starting any fasting routine, especially if with existing health conditions.

• Avoid extreme or prolonged fasting periods without medical supervision or adequate nutritional planning.

• Focus on balanced, nutrient-dense foods within any eating period, as food quality influences heart health as much as timing.

• Monitor your body’s response and adjust plans as needed, prioritizing sustainable habits over trends.

References

Study Citations

1. Zhong VW et al. “Time-restricted eating window and cardiovascular mortality in US adults: NHANES analysis.” Diabetes and Metabolic Syndrome: Clinical Research & Reviews, August 2025.

2. Sebastian SA et al. “Intermittent fasting and cardiovascular disease: A scoping review.” ScienceDirect, 2024.

3. American Heart Association Conference. “Preliminary findings on time-restricted eating and cardiovascular mortality.” AHA Lifestyle and Cardiometabolic Scientific Sessions, March 2024.

4. Almabruk BA et al. “The Role of Intermittent Fasting on Metabolic Syndrome.” Diabetes and Metabolic Syndrome, 2024.

Expert Interview Sources

• Victor Wenze Zhong, Senior Author, NHANES Study.

• Dr. Ranjan Shetty, Lead Cardiologist, Sparsh Hospital, Bengaluru.

• Dr. Anoop Misra, Chairman, Endocrinology, Fortis C-DOC.

Statistical Sources

• U.S. National Health and Nutrition Examination Survey (NHANES).

• Study population: 19,000 U.S. adults.

Additional Supporting Materials

• “A perspective on intermittent fasting and cardiovascular health.” Frontiers in Nutrition, January 2025.

• Horne BD et al. “Intermittent fasting and changes in clinical risk scores.” PMC, September 2023.

• Semnani-Azad Z et al. “Intermittent fasting strategies and their effects on body weight and metabolic risk.” BMJ, June 2025.

Medical Disclaimer

Medical Disclaimer: This article is for informational purposes only and should not be considered medical advice. Always consult with qualified healthcare professionals before making any health-related decisions or changes to your treatment plan. The information presented here is based on current research and expert opinions, which may evolve as new evidence emerges.