Groups Advised Against Fasting

1. Pregnant Women
   • Nutritional Needs: Pregnant women require additional nutrients to support fetal development. Fasting can interfere with the intake of necessary nutrients and increase the risk of nutritional deficiencies[2][6].
   • Dehydration Risk: The risk of dehydration is higher during pregnancy, especially in the third trimester, due to increased blood volume. Fasting can exacerbate this risk[2].
   • Potential Harm to Fetus: Fasting may lead to elevated cortisol levels, which can affect fetal development and increase the risk of cognitive impairment[6].
2. Lactating Mothers
   • Nutritional Requirements: Lactating mothers need a higher caloric intake to produce breast milk and maintain their own health. Fasting can reduce milk production and affect both maternal and infant health[4].
3. Young Children and Teens
   • Growth Needs: This group requires consistent nutrition for growth and development. Fasting can hinder these processes and lead to nutritional deficiencies[3].
4. Older Adults Experiencing Weakness
   • Health Risks: Older adults may have specific health concerns that require regular nutrition, such as maintaining energy levels and preventing muscle loss[3].
5. Individuals with Immunodeficiencies
   • Immune Function: Adequate nutrition is crucial for maintaining immune function. Fasting could compromise the immune system further[3].
6. People with Eating Disorders (Current or Past)
   • Psychological Impact: Fasting could trigger unhealthy eating patterns or worsen existing conditions related to eating disorders[3][10].
7. People with Dementia
   • Nutritional Needs: Dementia patients often have difficulty maintaining proper nutrition, and fasting could exacerbate these issues[3].
8. Individuals with a History of Traumatic Brain Injury or Post-Concussive Syndrome
   • Nutritional Support: Proper nutrition is essential for brain health, and fasting might impede recovery or maintenance[3].
9. People with Diabetes or Taking Certain Medications
   • Blood Sugar Levels: For individuals with diabetes, fasting can lead to dangerous drops in blood sugar levels (hypoglycemia). Those on medications that affect blood sugar or require food intake should also avoid fasting without medical supervision[7][10].
10. Cancer Patients Undergoing Active Treatment
    • Nutritional Support: Cancer treatments often require adequate nutrition to support recovery and maintain strength. Fasting could interfere with treatment efficacy and patient health[10].
11. People Who Are Underweight
    • Nutritional Deficiency Risk: Individuals who are underweight may not have sufficient reserves to safely fast without risking further weight loss and nutritional deficiencies[13].

These recommendations are based on general medical advice, but individuals should always consult healthcare professionals before deciding to fast, especially if they belong to any of these groups.