There is a rough ‘Formula of 3’ which says that one cannot live for 3 minutes without air, 3 days without water and 3 weeks without food. But this formula is applicable for healthy muscular people. When you fast you can stay healthy for long if you have good muscle mass and have adequate fat contents.
Minus points with Baba Ramdev: He has a thin muscle mass, his body fat content is low and moreover, he is fasting in summer.
Minus points with Baba Ramdev: He has access to AC environment, is a Yogi, who are known to fast for long by reducing the metabolic needs of their body.
Some salient points about fasting
Fasting is willingly abstaining from some or all food, drink, or both, for a period of time.
An absolute fast is abstinence from all food and liquid for a defined period.
Partially restrictive fast is limited to particular foods or substance.
The fast may also be intermittent in nature.
Fasting may also refer to the metabolic status of a person who has not eaten overnight, and to the metabolic state achieved after complete digestion and absorption of a meal.
A person is assumed to be fasting after 8–12 hours.
Metabolic changes toward the fasting state begin after absorption of a meal (typically 3–5 hours after a meal); "post–absorptive state" is synonymous with this usage, in contrast to the "post–prandial" state of ongoing digestion.
A diagnostic fast refers to prolonged fasting (from 8–72 hours depending on age)
The longest known fast for a human is 132 days (without food).
Snakes have been observed to go without food for up to 2 years.
Glucose is the body’s primary fuel source and is essential for the functioning of brain. When denied glucose for more than 4–8 hours, the body turns to the liver for glycogen, a storage form of glucose, to be used for fuel.
A process called glycogenolysis converts glycogen into a usable form of fuel. At this point, the body also uses small amounts of protein to supplement this fuel. This fuel will last for up to 12 hours before the body needs to turn to glycogen stored in muscles, lasting for a few more days.
If glucose is still denied at this point, muscle wasting is prevented by temporarily switching to fat as the fuel source, i.e. fat is converted into ketone through catabolism. Ketones, while not sugars, can be used by the brain as a fuel source as long as glucose is denied.
The body continues to use fat for as long as there is fat to consume.
The body will generally indicate to the fasting person as to when fat levels are running extremely low (less than 7% and 10% of body weight for males and females, respectively) with an increased urge for food. Fasts are usually broken long before this point.
If the fast is not broken, starvation begins to occur, as the body begins to use protein for fuel.
Health complications associated with fast–induced starvation include electrolyte imbalances, thinning hair, lanugo, cardiac arrhythmia and renal failure. Death can occur if fasting is pursued to the point of complete starvation.
Hypovolemia refers to any condition in which the extracellular fluid volume is reduced.
It can be produced by salt and water loss (as with vomiting, diarrhea, diuretics, bleeding, or third space sequestration) or by water loss alone (i.e., dehydration).
Salt and water loss comes primarily from the extracellular fluid whereas pure water loss (i.e., dehydration) comes from the total body water, only about 40 % of which is extracellular. Thus, for dehydration to produce the same degree of extracellular volume depletion as salt and water loss, 2.5 times as much fluid would have to be lost.
Patients with dehydration are always hypernatremic whereas those with salt and water loss typically have a plasma sodium concentration that is normal or even reduced (due to free water replacement of part of the deficit).
Prof. of Medicine, Govt. Medical College, AMRITSAR,PUNJAB