Risks and Alternatives to Extended Fasting

Potential Risks of Extended Fasting

The European Society for Clinical Nutrition and Metabolism (ESPEN) recommends against fasting during chemotherapy and other forms of diets that are not based on clinical evidence, due to the risk of malnutrition and micronutrient deficiencies in patients with or at risk of malnutrition 1
Extended fasting is specifically discouraged as it may increase the risk of inducing or aggravating malnutrition, particularly in vulnerable individuals such as those with existing medical conditions, cardiovascular disease, diabetes, or metabolic disorders 1
Individuals with existing medical conditions, such as cardiovascular disease or diabetes, are at higher risk of adverse effects from extended fasting, and should be advised against it 2, 3
People with a history of eating disorders should also be cautious when considering extended fasting, due to the potential for exacerbating their condition 1

Focus on improving overall diet quality, rather than extended fasting periods, is recommended for general health improvement, with Mediterranean-style diets having stronger evidence for health benefits 1, 6
Time-restricted feeding, limiting eating to a 6-12 hour window, may offer similar benefits to extended fasting with fewer risks, and has shown improvements in 24-hour glucose levels and markers of circadian rhythm 4, 5