A recent analysis presented by the American Heart Association has cast a shadow over the popular 16:8 intermittent fasting method, revealing that individuals who restrict their daily eating to an eight-hour window face a 91% increased risk of dying from cardiovascular disease. The study, which examined data from over 20,000 American adults, challenges long-held assumptions about the safety of time-restricted eating and has prompted doctors to warn three specific groups to avoid the diet entirely.
What Is 168 Intermittent Fasting?
The 168 fasting method, also known as intermittent fasting, involves a daily cycle of 16 hours of fasting followed by an eight-hour eating window. During the fasting period, only calorie-free beverages such as water, black coffee, or unsweetened tea are permitted. The rationale is straightforward: after the body depletes its stored glycogen—typically within 12 to 14 hours—it shifts to burning fat for energy, producing ketones and potentially aiding weight loss. However, the effectiveness of the diet hinges on what and how much is consumed during the eight-hour window. Overeating or choosing unhealthy foods can negate any benefits.
New Study Raises Red Flags
Researchers led by Dr. Wen Ze, a professor of epidemiology and biostatistics at Shanghai Jiao Tong University School of Medicine, analyzed dietary patterns from the 2003–2018 National Health and Nutrition Examination Survey (NHANES) and cross-referenced them with mortality data from the U.S. Centers for Disease Control and Prevention through December 2019. The findings, presented at an American Heart Association conference, revealed five startling facts:
- 91% higher risk of cardiovascular death among those who consumed all their food in less than eight hours daily.
- Increased cardiovascular death risk also observed in individuals with pre-existing heart disease or cancer.
- Among heart disease patients, eating within an 8-to-10-hour window was linked to a 66% higher risk of death from heart attack or stroke.
- Time-restricted eating did not reduce the overall risk of death from any cause.
- Cancer patients who ate over a 16-hour period showed a possible reduction in cancer-related death risk.
Dr. Wen Ze commented that while 168 fasting may offer short-term weight loss benefits, the study suggests it does not extend longevity and may carry serious long-term consequences.
Who Should Avoid 168 Fasting?
Separate medical reports have highlighted real-world dangers. A Taiwanese doctor previously shared a case of a man who developed gastric ulcers after three months of 168 fasting. Physicians now advise three categories of people to steer clear:
- Individuals with high energy demands – athletes, manual laborers, or those who burn many calories daily risk hypoglycemia and fainting.
- People with poorly controlled diabetes – erratic blood sugar levels can plummet dangerously during extended fasting.
- Those prone to binge eating – restricting eating to eight hours may lead to consuming two to three times the normal amount of food, undermining any health benefits.
The Bottom Line
The 168 fasting method remains popular for its simplicity and perceived metabolic advantages. However, this new research urges caution. Experts recommend consulting a healthcare provider before starting any time-restricted diet, especially for those with chronic conditions. Future studies are needed to clarify the long-term effects of intermittent fasting, but for now, the evidence suggests that a more moderate eating schedule—12 to 16 hours—may be safer for heart health.