Like vegetarianism, fasting has many variations and definitions. Some fasting protocols promote no solid foods but allow water and fruit juices, while others insist that allowing only water is a truer definition. Then there are those who neither eat nor drink for days on end. For the sake of clarity, the following explains the medical or physiological definition of fasting.
Fasting occurs naturally between meals (post-absorption) if food or nutrients are not consumed for three to five hours and after an overnight sleep (eight hours). During either of these times fasting is both required and safe, and part of an overall natural plan. Prolonged fasting is when no food or nutrients are consumed for 16 to 24 hours and continues for days or weeks. Depending on the individual's health and type of fast, prolonged fasting can be both counterproductive and dangerous.
Individuals who fast to lose weight are setting themselves up for failure because the body is hard-wired to combat starvation (prolonged fasting) due to evolutionary safeguards. In other words, during times of prolonged fasting the human body goes into self-preservation mode by slowing down metabolism and increasing the production of cortisol, known as the stress hormone. Cortisol is secreted by the adrenal glands in larger than usual amounts during times of illness, or emotional or physical stress, including starvation.
Cortisol breaks down muscle tissue in order to liberate certain amino acids (proteins) that can be converted to sugar to feed the brain, red blood cells and kidneys. Although the brain can utilize fats (ketones) for fuel as well as sugar, it prefers sugar, and red blood cells can only survive using sugar as their energy source. Breaking down muscle is counterproductive because muscle utilizes fat as its major source of energy, so losing muscle slows down the overall fat-burning process.
Prolonged fasting also decreases thyroid hormone production, and this, coupled with muscle tissue breakdown, slows down metabolic rate and overall metabolism. Sabotage comes into play once the fast is stopped and normal eating resumes – and most people do resume their normal eating habits. At the onset of prolonged fasting, appetite is suppressed, but once normal eating resumes, appetite hormones kick into full gear and individuals become hungrier. Increased appetite coupled with a slowed metabolism and less muscle tissue is the trifecta for weight gain.
The human body is an amazing machine designed to perform numerous involuntary functions, of which detoxification is of primary importance. In fact, the body has four very efficient organs designed to handle the detoxification of toxins: the skin, colon, liver and kidneys. In essentially healthy individuals, these organs function to rid the body of numerous toxins and waste products that could otherwise overwhelm us.
Other than being counterproductive, fasting for a short period (less than 24 hours) is safe. But prolonged fasting can break down muscle and deplete the body of valuable nutrients including vitamins, minerals and electrolytes, essential fatty acids, proteins and carbohydrates. Unhealthy individuals are at greater risk and should not fast other than normal fasting between meals and during sleep. Signs and symptoms of prolonged fasting include headaches, fatigue, dizziness and mental confusion, dehydration, hypoglycemia, constipation, feelings of coldness, gallstones, anemia and muscle weakness.
Whether you've put on the holiday pounds or want to improve your health by losing weight, consider the sensible approach of eating right and exercise before you put your body through the counterproductive stress caused by fasting.
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