Every January brings a familiar wave of detox promises with extended fasts, juice cleanses, one-meal-a-day routines, and multi-day water fasts marketed as quick fixes for weight loss and renewal. While
these trends are often framed as a way to reset the body after indulgence, extreme fasting rarely delivers lasting health benefits. From a gut health and longevity perspective, extremes tend to create more imbalance than repair, quietly compromising digestion, metabolism, and overall well-being.
Myth: Extreme Fasting Equals Detox
According to gut cancer surgeon and longevity consultant Dr. Arpit Bansal, the idea that fasting replaces the body’s detox systems is fundamentally flawed. “The human body already has a highly efficient detox system – the liver, kidneys, gut lining and immune system,” he explains.
He adds, “Fasting does not replace these systems. In fact, prolonged or aggressive fasting can stress the gut, especially when done repeatedly without proper refeeding.” The gut microbiome thrives on consistency, particularly dietary fibre. Dr. Bansal notes that beneficial microbes rely on fibre to produce short-chain fatty acids like butyrate, which protect the gut lining, regulate inflammation, and support immune balance. During extreme fasting, fibre intake drops sharply, disrupting this critical process.
When The Gut Microbiome Goes Into Survival Mode
Prolonged food restriction forces the gut microbiome to adapt, and not always in a healthy way. “When food intake is severely restricted, some bacteria begin feeding on the gut’s protective mucus layer. Over time, this weakens the intestinal barrier and increases the risk of leaky gut, inflammation, bloating, acidity and food intolerances,” Dr. Bansal says.
Dietitian and certified diabetes educator Dr. Archana Batra echoes this concern, adding that the gut is not designed to ‘rest’ from food. “One common myth is that the gut needs a break to cleanse itself. In reality, the digestive system functions best with regular nourishment. Prolonged fasting deprives gut cells of fuel, especially short-chain fatty acids produced when fibre is consumed,” she explains.
The Hidden Metabolic And Hormonal Costs
Beyond digestion, extreme fasting places significant stress on metabolic and hormonal systems. Dr. Bansal points out that very low calorie intake can disrupt cortisol rhythms, worsen sleep, and increase irritability and fatigue. Rapid weight loss associated with extreme fasting is also linked to gallstone formation, as the gall bladder does not contract normally when dietary fat intake is too low.
Dr. Batra highlights another overlooked effect: gut motility. “Skipping meals for long periods can slow digestion, increasing the risk of constipation and digestive discomfort,” she says. For individuals already dealing with stress, hormonal imbalances, or metabolic concerns, extreme fasting may further aggravate inflammation and cortisol levels.
A Longevity-Led Approach To Fasting
From a longevity standpoint, sustainability matters more than intensity. Dr. Bansal explains that intermittent fasting can be beneficial when done gently. “For most people, a fasting window of 12–14 hours, achieved by early dinners and slightly delayed breakfasts, is sufficient to support metabolic health without stressing the gut.”
While some individuals may tolerate 14–16 hours comfortably, fasting should always be personalised. If it disrupts sleep, digestion, mood, or performance, it stops being therapeutic.
Who Should Avoid Extreme Fasting
Both experts caution that extreme fasting is particularly risky for individuals with chronic acidity, IBS, a history of eating disorders, uncontrolled diabetes, gallstone risk, underweight individuals, pregnant women, or those recovering from illness or surgery.
Detox does not mean starvation. True gut health is built through stable blood sugar, adequate protein, sufficient fibre, hydration, electrolyte balance, and a resilient microbiome. Instead of chasing short-term detox trends, a gentle reset rooted in consistency supports digestion, metabolism, and long-term health far more effectively. In wellness and longevity, balance always outperforms extremes.
