Intermittent Fasting for Longevity

Intermittent fasting (IF) refers to eating patterns that cycle between periods of fasting and eating. Unlike traditional diets that focus on what you eat, IF focuses on when you eat.

Common IF approaches:

Time-Restricted Eating (TRE): Eating within a set window each day. - 16:8 — Fast 16 hours, eat within 8 hours (most popular) - 14:10 — Fast 14 hours, eat within 10 hours (gentler start) - 18:6 — Fast 18 hours, eat within 6 hours (more advanced)

Alternate Day Fasting: Alternating between regular eating days and fasting or very low calorie days.

5:2 Diet: Eating normally 5 days per week, restricting to 500-600 calories on 2 non-consecutive days.

Periodic Extended Fasts: 24-72 hour fasts done occasionally (monthly or quarterly).

Fasting Mimicking Diet (FMD): A 5-day protocol of very low calories designed to trigger fasting benefits while allowing some food.

Time-restricted eating (particularly 16:8) has the most research and is the easiest to sustain long-term. Most longevity researchers who practice IF use this approach.

Fasting triggers several biological mechanisms linked to longevity:

Metabolic Switching Fasting can promote metabolic switching—the shift from burning glucose to burning fat and producing ketones. The timing varies by individual, activity level, and prior diet, but generally occurs as glycogen stores deplete.

Autophagy Fasting stimulates autophagy—your cells' self-cleaning system. Damaged proteins and organelles are broken down and recycled. Autophagy declines with age; fasting may help restore it. Note: Precise autophagy timing in humans is not well-established and varies by context.

Reduced IGF-1 and mTOR Fasting reduces insulin-like growth factor 1 (IGF-1) and inhibits mTOR, a nutrient-sensing pathway. Lower IGF-1/mTOR signaling is consistently associated with longevity across species.

Sirtuin Activation The energy stress of fasting activates sirtuins—proteins involved in DNA repair, metabolism, and stress resistance. Sirtuins are key targets in longevity research.

Reduced Inflammation Fasting reduces markers of chronic inflammation, which drives aging and age-related diseases.

Animal evidence is strong: In virtually every species studied, some form of caloric restriction or fasting extends lifespan. Mice on intermittent fasting live 10-30% longer than ad libitum fed mice.

Human evidence is growing: While we can't do lifespan studies in humans, research shows IF improves biomarkers associated with longevity: insulin sensitivity, inflammation, blood pressure, and cholesterol.

Research supports several benefits of intermittent fasting:

Weight Management IF helps create a caloric deficit and may increase metabolic rate slightly. Most studies show comparable weight loss to continuous calorie restriction, with some finding better adherence to IF.

Insulin Sensitivity Fasting periods allow insulin levels to drop, improving insulin sensitivity. This may reduce diabetes risk and help manage existing type 2 diabetes (under medical supervision).

Cardiovascular Health Studies show improvements in blood pressure, cholesterol profiles (reduced LDL, increased HDL), and triglycerides.

Brain Health Fasting increases BDNF (brain-derived neurotrophic factor), supporting neuron health and potentially protecting against cognitive decline. Animal studies show neuroprotective effects.

Longevity Biomarkers In an observational cohort presented by Intermountain Health researchers, routine monthly fasting was associated with substantially lower mortality over follow-up (~45-49% lower risk). This is observational data and does not prove causality—confounding factors and healthy-user bias may play a role.

Cellular Repair Autophagy activation helps clear damaged cells and proteins, potentially reducing cancer risk and improving cellular function.

Important caveats: Most human IF studies are relatively short-term (weeks to months). Long-term effects in humans are still being studied. Individual responses vary significantly.

Conflicting evidence exists: Some observational data presented at AHA conferences has suggested potential risk signals for very short eating windows (e.g., less than 8 hours daily) in certain populations. This reinforces the need to individualize and avoid treating IF as a universal prescription. If performance, sleep, or menstrual regularity worsens, shorten your fasting window or discontinue.

Intermittent fasting isn't appropriate for everyone. Be aware of potential risks:

Common side effects (usually temporary): - Hunger, especially in first 1-2 weeks - Irritability and difficulty concentrating - Headaches (often from dehydration) - Lower energy initially

More serious concerns:

Hypoglycemia risk: People with diabetes taking insulin or sulfonylureas may experience dangerous low blood sugar. Never start IF without medical supervision if you're on diabetes medications.

Eating disorder risk: IF can trigger or worsen disordered eating patterns. If you have a history of anorexia, bulimia, or binge eating, IF may not be appropriate.

Nutrient deficiency: Compressed eating windows can make it harder to get adequate nutrition. Quality of food still matters enormously.

Hormonal effects: Some women report menstrual irregularities with aggressive fasting protocols. Women may do better with gentler approaches (14:10 vs 16:8).

Who should NOT do intermittent fasting: - Pregnant or breastfeeding women - Children and teenagers (still growing) - People with diabetes on certain medications (without medical supervision) - Those with history of eating disorders - People who are underweight - Those with certain medical conditions (consult your doctor)

Always consult a healthcare provider before starting IF, especially if you have any medical conditions or take medications.

If IF is appropriate for you, here's how to begin:

Week 1-2: Build up gradually Start with a 12-hour overnight fast (e.g., 7pm to 7am). This is what your body naturally does and helps you adjust to the concept.

Week 3-4: Extend to 14:10 Push breakfast later or dinner earlier to create a 14-hour fast. This is a sustainable long-term approach for many people.

Week 5+: Try 16:8 if desired If 14:10 feels comfortable, extend to 16:8. Many people skip breakfast, eating from noon to 8pm. Others prefer early eating (8am-4pm).

Tips for success:

- Stay hydrated: Water, black coffee, and plain tea are fine during fasts - Prioritize protein and fiber in your eating window to stay satisfied - Don't compensate by overeating during eating windows - Listen to your body: If you feel unwell, eat. This shouldn't be torture. - Be flexible: Social situations may require adjusting your schedule - Quality matters: IF isn't a license to eat junk food

When to eat matters too: Some research suggests eating earlier in the day (front-loading calories) may have additional metabolic benefits compared to late-night eating.

Track and adjust: Pay attention to energy levels, sleep quality, and how you feel. Not everyone thrives on IF—if it's not working for you after a fair trial, it's okay to try something else.