Fitness trainer Sara Kachhara recently went 13 consecutive days without food. “I voluntarily went 13 days without eating anything. The craziest part? I started with three days….and it kept on…around day 10-11, I could clearly feel the changes in my body to a point that I was creeped out by it. When I drank water, I could feel it churning in my stomach. I could hear my heartbeats. The interesting thing was not about the body but the mind,” she said in a post on Instagram.

How does fasting impact one’s body?

Gulnaaz Shaikh, clinical nutritionist at Healthyz, said fasting can change how the body uses energy, but a 13-day fast is very different from the shorter fasting patterns people commonly follow. “As food intake drops for an extended period, the body gradually shifts from using glucose as its main fuel to drawing more heavily on stored fat. Some people may report feeling lighter or less bloated, but that does not automatically mean that a prolonged fast is improving their health,” said Shaikh.

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The effects also depend on what “fasting” means in that particular case. “A person consuming water, electrolytes or some calories is in a very different situation from someone having no food at all,” remarked Shaikh.

What happens to the body during a prolonged fast?

Initially, the body relies on stored glycogen for energy. As these stores decline, fat becomes a more important fuel source and ketone production increases. “However, the body does not use only fat. With prolonged food deprivation, protein and muscle tissue can also be broken down,” said Shaikh.

Here’s what you should consider

That is where the concern lies. “The number on the weighing scale may fall, but some of that reduction can come from water and lean tissue, not simply body fat. Prolonged fasting can also affect energy levels, concentration, blood pressure and nutrient intake.”

Could someone feel better while fasting despite these concerns?

Yes, and that experience can be genuine. “Eating less may reduce bloating or digestive discomfort, while changes in fluid balance can make someone feel lighter. Some people also feel a sense of discipline or mental clarity that they associate with fasting. But feeling good during a fast is not enough to establish that it is safe or beneficial for everyone,” shared Shaikh.

 

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A post shared by Sara Kachhara (@withlovesaraa_)

Who should avoid attempting a prolonged fast without medical supervision?

According to Shaikh, people with diabetes, kidney or liver disease, a history of eating disorders, low blood pressure, nutritional deficiencies or other chronic conditions should not experiment with prolonged fasting on their own. Pregnant or breastfeeding women, children and older adults also have different nutritional requirements.

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If someone wants the benefits associated with fasting, what is a safer approach?

For most people, the focus should be on what they eat consistently rather than how long they can go without eating. “A sustainable eating pattern with adequate protein, vegetables, whole grains, healthy fats, and sufficient fluids is far more practical. If someone is interested in time-restricted eating or intermittent fasting, it is better to choose a moderate approach suited to their health, routine and nutritional needs rather than copying an extreme fasting challenge from social media,” said Shaikh.