What Does Not Eating Do to Body?

A close-up of a single legume on the prong of a fork.
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At the most basic level, food provides you with energy needed to maintain your heartbeat, breathing, organ function and basic mental activity. The body will cease to function after a few minutes without air and a couple of days without water. As long as they are properly hydrated, people can survive 30 to 40 days without food, Peter Janiszewski, Ph.D. stated in 2011 for The Public Library of Science's official blog. Avoiding food will eventually lead to mental confusion, extreme hunger, and the shutdown of vital organ and metabolic functions, followed by death if the situation is not corrected.

Food Restriction and Weight Loss

Not eating can result in dropping weight, but if your goal is weight loss, starving yourself is not the way to do it. According to the National Health Service, following a starvation diet is unsustainable and likely to backfire. While extreme restriction can lead to weight loss, it is also likely to cause cravings and eventual bingeing, which can lead to weight gain. If you want to lose weight, and keep it off, follow a sensible calorie restriction plan, eating natural foods in moderate amounts, and exercising moderately.

Loss Of Muscle Mass

One of the common effects symptoms of starvation is catabolism of lean protein, which is the breakdown of muscle fibers for use as energy. This is particularly pronounced in non-obese people, so if you are reasonably lean to begin with, you will lose more muscle mass as a consequence of starvation than if you had excess body fat. John E. Morley, MB, BCh, writing for The Merck Manual, said in 2013 that 25 percent to 50 percent of your initial weight can be lost during starvation.

Hormonal Disruption

The extreme weight loss associated with starvation can also cause serious disruption to endocrine function or normal patterns of hormone expression. People experiencing starvation show elevated levels of the stress hormone cortisol -- with more frequent release of the hormone and a longer effect. Various other hormones, including sex hormones and appetite hormones, are also extensively disrupted during starvation. These disruptions can cause anxiety, depression, irritability and fatigue in the starved person.

Organ Damage and Failure

Avoiding food can also cause damage to your organs, and in extreme cases, the organs can fail entirely. This is reasonably common in people with eating disorders, such as anorexia nervosa, in which food intake is severely limited. Common organ complications include heart problems such as slowed heart rate called brachycardia. Brain damage can also occur, resulting in seizures, confusion and nerve damage. In advanced stages of starvation, multiple organ failure can occur.