Many of today’s most common health conditions – high blood pressure, type 2 diabetes, fatty liver disease, and even some autoimmune disorders – are driven by dietary excess. Too many calories, too much visceral fat, and constant exposure to processed foods keep the body in a state of inflammation. Fasting, whether short daily intervals or longer supervised fasts, works as a reset. It shifts the body’s fuel source, reduces visceral fat, activates cellular housekeeping, and helps restore balance. Below is a chronological timeline of what happens during fasting and how it can be applied practically.

0 to 12 hours: the post-meal phase
Your body runs on glucose from your last meal. Insulin is elevated, storing surplus energy as liver glycogen and body fat. This is a good window to avoid snacking, walk lightly, and allow insulin levels to settle.

12 to 24 hours: glycogen winds down, ketones rise
Liver glycogen begins to deplete. Ketones are produced and the brain slowly shifts to using them as fuel. Extending the overnight fast to 12 hours or more is a simple way to enter this phase.

24 to 36 hours: the fuel switch gathers pace
Beta-hydroxybutyrate, a primary ketone, rises and fuels the brain. Energy feels steadier. Hunger often fades. This is where supervision matters if you take medication that lowers blood sugar or blood pressure.

36 to 48 hours: stable ketosis, brain benefits
The brain now runs largely on ketones. BDNF (brain-derived neurotrophic factor) increases, supporting brain health and cognitive clarity. Appetite usually remains suppressed, but salt and hydration need attention.

Days 3 to 4: autophagy and inflammation drop
The body intensifies autophagy, clearing damaged cells and waste. Visceral fat, the harmful fat around organs, is broken down. Blood pressure and fasting glucose often improve significantly. Rest is important to protect lean muscle.

Days 5 to 7: metabolic clean-up and palate reset
Fat loss accelerates, the gut microbiome dips, and taste sensitivity recalibrates. Many people find whole foods taste better after this phase. Annual 5–7 day supervised fasts can act as resets for otherwise healthy individuals.

Days 8 to 14: deeper clinical benefits
Hypertension, insulin resistance, fatty liver disease, and some autoimmune conditions respond strongly here. Weight loss averages ~1 pound per day, with a higher share from visceral fat. Close monitoring is vital.

Weeks 3 to 6: therapeutic range only
Extended fasting is reserved for specific clinical cases. Blood pressure, blood sugar, and autoimmune symptoms can improve further, but electrolyte balance becomes fragile. This should only be attempted with professional oversight.

Refeeding: half the length of the fast
Refeeding is as important as fasting. Begin with diluted juices, progress to raw produce, then add cooked vegetables and starches. A structured plan prevents refeeding syndrome and rebuilds a healthier gut microbiome.

After refeeding: consolidate the win
Expect some weight rebound from water, glycogen, and gut contents, while fat loss continues. Use the taste reset to maintain a whole-food diet, adequate sleep, and daily movement.

Daily rhythm: the sustainable option
Most people benefit from 12–16 hours of fasting daily. A 16:8 pattern helps with weight control and appetite, while athletes or highly active people may need a longer eating window.

Cognition and mood: why focus improves
Fasting stabilises blood sugar, avoiding the highs and crashes of refined carbohydrates. Many people report sharper focus, more creativity, and a calmer mood when fasting.

Women’s health: cycles and PCOS
PCOS and other hormone-related conditions often improve with fasting due to reduced insulin resistance and visceral fat. However, excessive weight loss can disrupt menstrual cycles. Individualisation and supervision are essential.

Safety checkpoints
Not everyone should fast. Pregnant or breastfeeding women, those with eating disorders, advanced kidney disease, uncontrolled medical conditions, or those on certain medications should avoid prolonged fasts without medical clearance.

A simple starting plan
• Try a 12 to 14-hour overnight fast for two weeks.
• Eat three whole-food meals, avoid late-night calories, and hydrate with water.
• Walk daily and sleep well.
• If suitable, experiment with a 16:8 fasting window several days per week.
• For longer fasts beyond 24 – 48 hours, seek medical supervision.

Disclaimer
This article is for informational purposes only and is not a substitute for medical advice. Fasting affects metabolism, electrolytes, and medication needs. Always consult a qualified healthcare provider before beginning any fasting program, especially if you have pre-existing health conditions or take prescription medications.