Without water, you can survive only a few days. However, you can go for weeks without food. That’s because your body is very resourceful. It can get energy and fuel from its own fat. It can also draw on muscle reserves when needed.
Still, the time frame for survival without food cannot be accurately estimated. There is no solid scientific data to answer this question. This is because ethics prevent scientists from studying starving people.
Every person is different. Personal factors such as initial weight may play a role. Therefore, it can be difficult to answer this question.
The human body is quite resilient and can go days and weeks without proper food and water. This is not to say that it is healthy or should be practiced to go without food for an extended period of time.
The body can go without food and water for a week or two, and possibly even longer if water is taken. Those who starve themselves need to be monitored by a doctor to recover after the period without food to avoid refeeding syndrome.
How is that possible?
Living for days and weeks without food and water seems unimaginable for many of us. After all, a day or even an hour without food and water can leave many of us irritable and lacking energy.
The body adapts to fasting for short periods of time or to not having food and water for long periods of time. So people can practice religious fasting and even try fasting diets like the stop eating method without doing irreparable damage to their bodies.
It takes about eight hours without eating for the body to change the way it functions. Before that, it functions as if you were eating regularly. Under normal circumstances, the body breaks down food into glucose. The glucose provides the body with energy.
When the body has not eaten food for 8 to 12 hours, the glucose stores are depleted. The body then begins to convert glycogen from the liver and muscles into glucose.
When glucose and glycogen are depleted, the body begins to use amino acids for energy. This process affects your muscles and can keep your body going for about three days before the metabolism makes a major switch to maintain lean body tissue.
To prevent excessive muscle loss, the body begins to create ketones from fat stores for energy, a process called ketosis. During this time, you will experience significant weight loss. One of the reasons why women can last longer on a starvation diet than men is that their bodies have a higher fat composition. Women are also able to store protein and lean muscle tissue better than men during starvation.
The more fat stores there are, the longer a person can usually survive during starvation. Once fat stores are completely depleted, the body reverts to muscle breakdown for energy, as this is the only remaining fuel source in the body.
During the starvation phase, when the body uses its muscle reserves for energy, severe negative symptoms occur. A study in the British Medical Journal Trusted Source states that people who undergo starvation should be closely monitored for severe side effects of starvation after losing 10 percent of their body weight. It also states that very serious conditions occur when a person loses 18 percent of their body weight.
If you do not eat for a week, but drink water, take salt, vitamins and minerals:
- Your body temperature will drop a bit because ATP production will be reduced, brown fat will no longer generate excess body heat, etc.
- Partially damaged cells will be broken down and replaced more quickly to improve efficiency. This can reduce senescence and other signs of cell aging.
- Growth hormone levels increase. This is an adaptation to spare proteins for tissue repair instead of converting them into fuel.
- Your hunger will probably go away after a few days, but if you are exposed to the smells of your favorite foods, you may crave them. This varies from person to person.
- Your sense of alertness and awareness may change. Some people get a little dizzy, others feel like things are clearer. Some people have difficulty with higher order long-term thinking, others feel stimulated.
- Peak physical performance decreases because anaerobic capacity is significantly reduced. Glycogen stores drop to lower levels, and your body conserves glucose wherever possible. Glucose is reserved for red blood cells (can’t use other fuels) and some types of brain cells, and is otherwise shuttled back and forth as an energy source through pyruvate and lactate cycles. Some of it is replenished from glycerol released during fatty acid metabolism; however, not enough of it is produced during prolonged water fasting.
- Your body will convert some of the muscle tissue into carbohydrates to maintain glucose reserves. For one week, this is usually not significant and can be compensated for by normal strength training during the refeeding week. For longer fasts, this process accelerates somewhat.
It is important to know that medical fasts over 1-2 days are usually not calorie free. Fasting over 2 to 4 days usually has 200 to 300 calories, and fasting over 5 days usually has 500 calories (also known as ultra-low calorie diets). These diets are usually specially structured to provide adequate protein, specific nutrients, etc., but are low enough in calories to provide the same metabolic benefits as fasting. Zero-calorie fasting can cause refeeding syndrome if it lasts longer than 2 weeks, but 500-calorie fasts have been done for more than a year in the most extreme cases. You may find that 500-calorie diets are sufficient to alleviate the unpleasant side effects of zero-calorie diets, and they can be a good way to prepare for a water fast if that is a specific goal you have.
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