Intermittent Fasting: The Balance Between Benefit and Burnout

By Dr D Michael Elliott MSc D.C. CFMP Lifestyle Medicine Practitioner & Chiropractor

Why Intermittent Fasting Became So Popular

Intermittent fasting (IF) has become one of the most talked-about nutrition and longevity strategies in recent years — and for good reason. When done correctly, fasting can help:

• Regulate insulin and blood sugar

• Reduce inflammation and oxidative stress

• Support healthy body composition

• Enhance cellular repair and mitochondrial efficiency

• Promote mental clarity and focus

These benefits stem from giving the digestive system a rest and allowing the body to switch from a “fed” to a “repair” state — a process called metabolic switching.

However, as with most health trends, more is not always better. In Functional and Lifestyle Medicine we frequently see patients who have over-fasted, under-nourished, or chosen the wrong fasting strategy for their body type or health status.  The result can be metabolic imbalance, hormonal stress, and burnout — the very opposite of what fasting is meant to achieve.

How Fasting Works — and Why Balance Matters

When we stop eating for a period (typically 14–18 hours), insulin levels fall and the body begins to mobilize stored fat for energy.In moderation, this shift:

• Improves insulin sensitivity

• Increases fat oxidation

• Encourages autophagy, the clean-up of damaged cells

But beyond a certain point, prolonged or excessive fasting can signal the body that energy scarcity is occurring.  The brain, adrenals, and thyroid all interpret this as stress, triggering:

• A rise in cortisol (stress hormone)

• Reduced thyroid T3 production (to conserve energy)

• In women, reduced reproductive hormone signalling

• In some, compensatory binge-eating once the fast ends

The Hidden Pitfalls of Over-Fasting

1. Adrenal and Cortisol Overload

Too long without fuel raises cortisol, keeping the body in “fight-or-flight” mode. Chronic cortisol elevation increases cravings, disrupts sleep, and can blunt testosterone or progesterone production.

2. Thyroid Suppression

Prolonged fasting or very low-carb intake reduces T3 (active thyroid hormone). Over time this slows metabolism, leading to fatigue, cold intolerance, and difficulty maintaining weight loss.

3. Blood-Sugar Instability

Some people — particularly those with reactive hypoglycemia, diabetes medications, or high stress levels — can experience sharp drops in glucose, dizziness, or anxiety during long fasting windows.

4. Hormonal Disruption in Women

Women’s hormonal systems are more sensitive to energy availability. Extended fasting or calorie restriction can alter estrogen-progesterone balance and affect menstrual regularity, fertility, and mood.

5. Reduced Muscle Mass

Without adequate protein feeding windows or resistance training, fasting can accelerate muscle breakdown — lowering metabolic rate and strength.

Who Should Be Cautious or Avoid Intermittent Fasting

Intermittent fasting may not be appropriate — or should be supervised — in individuals who:

• Have thyroid, adrenal, or blood-sugar disorders

• Experience anxiety, low mood, or sleep disturbance

• Are pregnant, breastfeeding, or under 18

• Have a history of eating disorders or chronic under-eating

• Are taking insulin or glucose-lowering medications

In these cases, fasting may add metabolic stress rather than resilience.

How to Fast Safely and Effectively

1. Start gently: Begin with a 12:12 or 14:10 schedule (fasting hours : eating hours) and extend only if well-tolerated.

2. Stay hydrated: Water, herbal teas, or electrolytes during fasting hours prevent fatigue and headaches.

3. Prioritize nutrient density: Break the fast with balanced meals containing quality protein, healthy fats, and colourful vegetables.

4. Support the adrenals: Ensure adequate sleep, manage stress, and consider adaptogens or minerals like magnesium if indicated.

5. Cycle your fasting: Include “re-feed” days or weeks of relaxed eating to reassure hormonal and metabolic pathways.

6. Listen to biofeedback: Persistent fatigue, irritability, poor sleep, or hormonal changes mean the fasting window is too long for your physiology.

The Take-Home Message

Intermittent fasting can be a powerful metabolic and longevity tool — but it must be individualized. When performed moderately, with proper nutrition and rest, it enhances cellular repair and energy regulation. When pushed too far or applied to the wrong physiology, it can create the very imbalances we aim to correct.

If you’re considering fasting as part of your health strategy, work with a Functional or Lifestyle Medicine practitioner who can tailor the approach to your hormones, nutrient status, and stress physiology.

References available on request. This article is for educational purposes only and not a substitute for individualized medical advice.