Intermittent fasting (IF) has gained widespread popularity as a dietary approach for weight loss and potential health benefits, such as improved insulin sensitivity and inflammation reduction. It involves cycling between periods of eating and voluntary fasting. However, the health benefits touted by proponents do not apply to everyone, and for certain individuals, IF can be dangerous or even life-threatening. Medical experts widely agree that certain populations should avoid this eating pattern altogether.
Primary Groups Who Should Not Do Intermittent Fasting
For several key demographics, the risks associated with intermittent fasting far outweigh any potential rewards. The following groups are strongly advised against attempting this diet without explicit medical clearance and supervision.
Individuals with a History of Eating Disorders
Intermittent fasting's inherent emphasis on food restriction and controlling eating windows can be a significant trigger for those with a history of or a predisposition to eating disorders, such as anorexia nervosa, bulimia, or binge eating disorder. The mindset required for fasting can reinforce unhealthy, restrictive behaviors and thought patterns around food. The Butterfly Foundation, an organization dedicated to eating disorder support, does not endorse fasting diets for this reason. The practice may lead to a cycle of restriction followed by binging, further complicating recovery or worsening the condition.
Pregnant and Breastfeeding Women
Women who are pregnant, trying to conceive, or breastfeeding should not engage in intermittent fasting. These periods of life require a consistent and nutrient-rich energy supply to support both the mother's health and the baby's proper development.
- Pregnancy: During pregnancy, a woman's body needs extra calories and nutrients. Calorie restriction can place undue stress on the body and potentially endanger the developing fetus. Some studies suggest fasting may also reduce a person's chances of becoming pregnant.
- Breastfeeding: The production of breast milk is an energy-intensive process, requiring an additional 350-500 calories daily. Fasting can lead to a reduced milk supply, fatigue, and dehydration, all of which are detrimental to both the mother and the nursing infant.
People with Diabetes
For individuals with diabetes, particularly those with Type 1 or Type 2 who take insulin or other glucose-lowering medications, intermittent fasting can be extremely dangerous. The risk of life-threatening hypoglycemia (dangerously low blood sugar) is a major concern during extended fasting periods.
- Hypoglycemia Risk: Fasting dramatically alters blood sugar levels. For those on medication, this can lead to an unsafe drop in glucose, causing dizziness, confusion, seizures, or loss of consciousness.
- Medication Adjustments: Any fasting regimen would require precise adjustments to medication, which must be carefully managed by a healthcare provider. Some diabetes medications, like metformin, also need to be taken with food to prevent stomach irritation.
- Diabetic Ketoacidosis (DKA): People with Type 1 diabetes and some with Type 2 are at risk of DKA, a serious complication where the body produces dangerously high levels of ketones, which can result from prolonged fasting.
Other Medical and Health Considerations
Beyond the primary groups, several other medical conditions and situations warrant caution or complete avoidance of intermittent fasting.
Older Adults and Underweight Individuals
For older adults, particularly those who are frail or have chronic health issues, intermittent fasting can be risky. There is less evidence on its long-term effects in this population, and concerns exist about the potential for excessive weight loss, which can lead to a loss of muscle mass, weakened immune function, and bone density issues. Underweight individuals also should avoid IF, as it could further compromise their health by leading to insufficient nutrient intake.
People Taking Certain Medications
Many medications must be taken with food to prevent nausea, stomach irritation, or to ensure proper absorption. Intermittent fasting, especially with its extended fasting windows, can interfere with medication schedules and effectiveness. Those taking blood pressure or heart disease medications, NSAIDs, steroids, or thyroid medication should consult their doctor to determine if IF is feasible and to adjust dosage and timing.
Cardiovascular and Blood Pressure Issues
While some short-term studies have shown IF can lower blood pressure, new research has correlated an eight-hour eating window with a higher risk of cardiovascular death over the long term, particularly for those with existing heart disease. Furthermore, individuals with hypotension (low blood pressure) may experience a drop in blood pressure during fasting, leading to symptoms like dizziness, lightheadedness, and fainting.
Gastrointestinal Sensitivity and Sleep Problems
Individuals with sensitive bowels or conditions like irritable bowel syndrome may find that intermittent fasting worsens digestive issues such as bloating, constipation, or indigestion. Additionally, going to bed hungry can disrupt the circadian rhythm and interfere with sleep, which is crucial for emotional stability and overall health.
Physically Active Individuals and Athletes
Athletes or people with rigorous training schedules may find it difficult to get sufficient calories and nutrients within a restricted eating window to fuel their workouts and recover properly. This can lead to fatigue, low energy, and poor athletic performance.
Intermittent Fasting: Is It Right for You? A Comparison
| Feature | Healthy Adult | Individual with Contraindications |
|---|---|---|
| Potential Benefits | Weight loss, improved insulin sensitivity, reduced inflammation. | Potentially harmful side effects, including severe blood sugar fluctuations, malnutrition, and psychological distress. |
| Risks | Mild side effects like hunger, headaches, and fatigue during the adjustment period. | High risk of severe health complications, including life-threatening hypoglycemia, relapse of eating disorders, and nutrient deficiencies. |
| Suitability | Safe for most healthy individuals after medical consultation. | Not recommended and can be dangerous due to underlying health conditions or specific life stages. |
| Medical Supervision | Recommended for personalized guidance. | Absolutely mandatory, with high-level monitoring and careful planning if attempted. |
How to Proceed Safely
For anyone considering intermittent fasting, the first step should always be a consultation with a healthcare professional or a registered dietitian. This is especially true if you fall into any of the high-risk categories. A doctor can assess your overall health, review your medical history, and help you determine if a modified approach or an alternative diet is safer and more appropriate for your specific needs. For example, if you have diabetes, a doctor can help monitor blood sugar levels and adjust medication to mitigate the risk of hypoglycemia. Ignoring these warnings could lead to serious, and in some cases permanent, damage to your health.
Conclusion
While intermittent fasting can be a viable and beneficial nutritional strategy for many, it is not a universally applicable diet. The decision to undertake IF should be made with careful consideration of individual health status, medical history, and life circumstances. The most prominent groups who should not do intermittent fasting include individuals with a history of eating disorders, pregnant or breastfeeding women, and those with diabetes, due to the high potential for significant health complications. Other considerations include age, current medication use, and preexisting heart or blood pressure conditions. The foundation of any healthy diet remains prioritizing nutrient-dense foods and listening to your body's signals, and this is even more crucial for those with risk factors. Always consult a healthcare professional before making significant changes to your eating patterns to ensure your safety and well-being. A great resource for further reading is the Mayo Clinic, which provides reliable health information on a variety of topics, including intermittent fasting.
