What Happens To Your Body When You Fast Once Weekly? Doctor Answers

Intermittent fasts have become popular which involves cycling between eating and fasting. With intermittent fasting, you only eat during a specific time. Some of the most popular ones are 16:8 fasting (fast for 16 hrs and eat in an 8 hr window), 14:10 fasting, 5:2 diet (eat normally 5 days and very low calories for 2 days), and 24-hour fast (once or twice weekly), among others. Most people tend to follow the 16:8 fast or the 14:10 fast. Johns Hopkins Medicine says that these diets are "known to have several health benefits, which includes reduced calorie intake, improved blood sugar levels, lower body weight, better cellular repair, and others. However, it is important that you follow these diets under medical supervision."

Speaking to NDTV, Dr. Amit Prakash Singh, Consultant - Internal Medicine at the CK Birla Hospital, Delhi, said, "I'm not referring to starving yourself or skipping meals daily, but simply taking a 24-hour break from eating. Let me break it down for you. When you eat, your body uses glucose (sugar) for fuel. Some of this sugar is stored in your liver as glycogen, and this typically lasts for about 12 hours. Once these stores are depleted, your body will switch from using sugar to using fat for fuel. This fat is then converted to ketones, which are an alternate fuel source for your brain and heart. Therefore, fasting can help you lose belly fat and lower blood sugar."

Benefits Of Fasting Once Weekly

1. Energy Source

Within 10-14 hours, your liver's glycogen reserves are depleted, which forces your body to switch from glucose to stored fats for energy. Ketones are an alternative brain fuel, which stabilises energy without the spikes. This process, called ketosis, boosts fat breakdown while growth hormone surges to protect muscle tissue from being used as fuel. When this fast is done repeatedly, your body becomes more efficient at this switch, improving overall fat-burning capacity.

2. Blood Sugar Regulation

Blood glucose levels typically drop during the fast, leading to a sharp decline in insulin. This improves insulin sensitivity, helping cells respond better to the hormone and reducing risks for type 2 diabetes. "Lower insulin levels can help you better regulate your blood sugar levels and may even lower your risks of weight gain and type 2 diabetes," said Dr. Prakash Singh. People with prediabetes often see notable improvements in blood sugar levels after just a few cycles.

3. Hormonal Responses

Stress hormones like cortisol peak, increasing focus and alertness during the fast. Meanwhile, human growth hormone levels increase which helps in fat mobilisation and muscle preservation. Feel-good chemicals like endorphins and serotonin also rise, which helps to keep away irritability and foster a sense of calm after the fast.

4. Cellular Repair Activation

When you fast for a day, autophagy kicks in, which is a process where cells recycle damaged proteins and organelles. This cleanup helps to increase longevity, reduce inflammation, and improve pancreatic function by clearing excess insulin-producing components. Weekly fasting triggers these benefits without the exhaustion of longer fasts. Dr. Prakash Singh, "Fasting also stimulates the body's natural processes to clean out and recycle damaged cells."

5. Weight Management

You'll likely lose 1-1.7 kg temporarily from water and glycogen depletion. However, you'll lose weight gradually when you stick to your weekly fasts. You might see your waistline slim down by a couple of centimeters over weeks.

6. Cardiovascular Benefits

The fast contributes to better heart health markers. Triglycerides and blood pressure often decrease, while HDL cholesterol inches up. Diastolic pressure may dip noticeably, which reduces vascular strain. Though LDL cholesterol can rise temporarily due to fat release, it stabilises with consistency.

7. Brain and Mood Effects

Ketones are a steady fuel source for the brain, which potentially enhances mental clarity. Hunger often fades mid-fast due and endorphin boosts can improve mood. Early sessions might cause mild fatigue or brain fog, but hydration and electrolytes can be helpful. In the long-term, this practice may help stabilise cognition by reducing metabolic stress.

8. Digestive and Gut Reset

Your gut gets a break when you fast once a week. This allows the intestinal lining to repair and beneficial microbes to rebalance. Reduced eating also helps to ease the digestive workload, potentially alleviating bloating or irregularity. Hence, when you eat again, nutrient absorption improves as the system "reboots".

"Many people have noticed that they feel lighter, more energetic, and mentally alert after fasting. However, fasting is not recommended for all people. Pregnant women, older people, people with chronic diseases, and those who are taking insulin or certain medications should not fast. If you are fit for fasting, make sure that you drink plenty of fluids and do not overeat when you break your fast. If done properly, fasting once a week can help promote good health," adds Dr. Prakash Singh.

Disclaimer: This content including advice provides generic information only. It is in no way a substitute for a qualified medical opinion. Always consult a specialist or your own doctor for more information. NDTV does not claim responsibility for this information.