Ramadan 2026: What happens to your body during fasting? Bengaluru doctor says 'body shifts to burning fat for energy'

Every year, millions of Muslims around the world observe Ramadan by fasting from dawn to sunset. While the practice is rooted in faith and discipline, it also sets off a series of biological changes inside the body — changes that doctors say are both predictable and, for most healthy adults, safe when managed properly.

According to Dr Suchismita Rajamanya, Lead Consultant and Head of Internal Medicine at Aster Whitefield Hospital, Ramadan fasting prompts the body to shift how it produces energy.

“Within a few hours of fasting, the body stops relying on sugar and begins using stored fat for energy. This metabolic switch is natural and not harmful in healthy individuals,” she explains.

“After glycogen is depleted, the body turns to fat stores. This is what many people refer to as ‘fat burning’, and it’s a normal survival response,” Dr Rajamanya says.

This transition — known as metabolic switching — may also improve how the body responds to insulin. “Short, controlled fasting periods can help the body handle sugar more efficiently, especially in people without underlying metabolic disease,” she adds.

During Ramadan, meal timing shifts significantly, with suhoor before dawn and iftar after sunset. While this schedule is manageable, Dr Rajamanya cautions against heavy late-night meals.

“Eating large portions late at night and sleeping poorly can blunt the metabolic benefits of fasting. Sleep disruption affects hormones that regulate appetite and energy,” she says.

Maintaining regular sleep hours and keeping iftar balanced, she notes, is just as important as the fast itself.

“Most healthy kidneys adapt well, but dehydration is common in hot climates or during long summer fasts,” Dr Rajamanya says. “Headaches, dizziness, fatigue and dark urine are early warning signs people should not ignore.”

She advises people with kidney disease, heart conditions, or diabetes to seek medical guidance before fasting.

“Weight changes depend less on fasting and more on what and how you eat at iftar and suhoor,” Dr Rajamanya explains. “Meals should include protein, fibre and healthy fats to prevent overeating at night and energy crashes during the day.”

Brain Function And Energy Levels

Headaches, irritability and low energy are common during the first few days of fasting, but these symptoms are often misunderstood.

“Most early discomfort comes from caffeine withdrawal and sleep disruption, not fasting itself,” she says. “Once the body adapts, energy levels usually stabilise.”

“Some people see improvements in cholesterol levels, but this depends entirely on food choices during Ramadan,” Dr Rajamanya notes.

“In some cases, adjusting medication timing or choosing not to fast is the safer option,” she says.