Fasting can be hazardous to health if not taken proper care during the process. People do fasting for various reasons and among them, they could be weight loss, health, religion or finance. Fasting can be of various types such as juice only fast and the other is dry fast which excludes all liquids and food.
Fasting can have some health beneficial effects, but they can be very dangerous as they have negative impacts in short and long term. It can also lead to detrimental effects in many people, especially in those who want to lose weight. Abstaining away from food depend mainly on the person who is fasting. The side effects of fasting can be better understood in the following lines.
Fasting removes the toxins in the body and other harmful substances. It helps the immune system to work better, burns up fat, increases energy. It also helps in the treatment of several illnesses such as acne, arthritis, allergies, cancer, high blood pressure, asthma etc.
Fasting is also done for religious reasons in some countries, particularly in the East. Many abstain from food in order to fulfill their hopes and desires. They believe that fasting will purify the soul and appease God.
Impact of Fasting On The Body
When a person in on fasting, his body is devoid of new supplies of protein, carbohydrates, vitamins and minerals, except the vitamin which he gets from water. Levels of energy sources during fasting can be understood in the following points:
- When the body has consumed all the energy available in the food, then it turns to the carbohydrate reserves in the body
- Thus, it is vital to know when your body runs out of these stores because at that time, the energy has to be obtained from other resources to perform basic actions such as walking and breathing
- When the reserves of carbohydrates are used up by the body, then it will turn to the protein reserves which implies to muscle mass and ultimately, the organs
So, at this point when the fast is ended, the person is technically at the starvation stage.
Top 5 Side Effects of Fasting
Side effects of fasting can be divided into the following categories:
1. Side Effects of Weight Management
People who do fasting for losing weight are especially prone to gaining weight:
- According to dietitians registered with Mayoclinic.com, research reveal that after a period of fasting, people tend to crave for more starchier food which contain high calories
- The basic source of the body for fuel is carbohydrates and extreme hunger leads to consume more calories in just one sitting, which is quite hazardous to health. Thus, this reverses the intended effect of weight management plan through fasting
- You might tend up losing some weight due to fasting, but you return to the previous weight as soon as you stop fasting. This sudden change in weight is not good for heart health
2. Short Term Side Effects
There are various short term side effects of fasting and they may include:
- Dizziness
- Headache
- Fatigue
- Light headedness
- Abnormal heart rhythms
- Low blood pressure
- The person who is on fasting might not be able to perform certain tasks such as driving a vehicle or operating a machine
- Some short term side effects can also include flaring up of gallstones or gout
- They may also include inability of body to absorb some medications or it can also alter interaction of drugs in the body
3. Long Term Side Effects
Fasting can be very dangerous as far as long term side effects are concerned. These are discussed in the following points:
- Fasting can cause damage to immune system of the body
- Many body organs can also get affected by fasting which may include kidneys and the liver
- Important body functions can also get hampered
- Fasting can be very dangerous for a person who is already malnourished, such as cancer patients and they should never do fasting
- Long term side effects of fasting can even include death when the reserve of the body is completely depleted
4. Dry Fasting Side Effects
Some people adopt dry fasting for immediate results and thus, they abstain from consuming any liquid or food which is quite dangerous. Dry fasting can lead to the following symptoms in the body:
- It can cause dehydration and ultimately death in a few days
- According to American Cancer Society, health impact due to dry fasting depends on the individual and context
- Some external factors such as heavy exertion, heat and compromised health can cause dry fasting to be lethal in a matter of few hours
5. Stomach Problems
Fasting can result in severe side effects as the stomach acids can burn the inner lining of the intestines. If the stomach is kept empty for longer duration, the acids produced in the intestine can burn the lining and cause acidity. Fasting that include laxatives can lead to extreme water loss and malnutrition.
Hence, absolute fasting is never recommended, water fasting and juice fasting can be done but under medical supervision as the above lines show how side effects of fasting can affect a person’s health. Long duration fast are not at all recommended, instead under 48 hours fast are advisable at all times. Thus, fasting occasionally in safe manner helps improve protein synthesis and improves energy level. Pregnant and breastfeeding women should avoid fasting and also persons under medication, having heart problems must stay away from fasting.
FAQ
1) Does fasting impact exercise performance?
Often, yes. Training while fasting can lower available energy, making workouts feel harder. A 2020 sports nutrition review found that performance dropped in high-intensity activities without fuel
(NIH). You may notice slower reaction time, reduced endurance, or early fatigue. Light activity, like walking or stretching, is usually fine. Athletes often have eating windows to support training. Listen to your body; pushing too hard while under-fueled can raise injury risk.
2) How does fasting influence hydration levels?
Fasting can lead to dehydration, especially if no liquids are consumed. The body loses water through breathing, sweating, and urination. A 2% fluid loss can affect focus and mood (CDC). Signs include headache, dizziness, and dry mouth. Rehydrating after fasting is essential. Choose water or electrolyte-rich drinks before breaking the fast with solid foods. Hydration is just as critical as food for overall health.
3) Could fasting affect mood or mental sharpness?
Yes. Low blood sugar during fasting may cause irritability, difficulty concentrating, or a short temper. The brain runs mainly on glucose. When levels drop, focus can suffer. A study in the Journal of Nutrition linked even mild fasting to slower reaction times (NIH). For some, mood dips within hours; others adapt over days.
Breaking the fast with balanced food can restore mental clarity and lift mood quickly.
4) Is fasting safe for older adults?
It depends on overall health. Older adults may have medical conditions or take medicines that make fasting risky. Low blood sugar, dehydration, and dizziness increase fall risk. A 2019 review found calorie restriction affected muscle strength in seniors (NIH). Without adequate nutrition, recovery from illness or surgery can be slowed. A healthcare professional should monitor any fasting plan for older adults to prevent harm and maintain muscle and bone health.
