ntake of carbohydrates, fats, and proteins provides energy that can be used to perform various body functions or stored for later use. Stability of body weight and composition over long periods requires that a person's energy intake and energy expenditure be balanced. Loss of body mass and starvation occur when energy intake is insufficient to meet the body's metabolic needs.
Glucose is the primary substrate for energy in tissues such as the brain and red blood cells, and adequate amounts of glucose must be present in the blood for several hours between meals. The liver plays a key role in maintaining blood glucose levels during fasting by converting its stored glycogen to glucose (glycogenolysis) and by synthesising glucose, mainly from lactate and amino acids (gluconeogenesis). Diminished carbohydrates in the cells and decreased blood sugar are the basic stimuli that increases the rate of gluconeogenesis.
Release of epinephrine and norepinephrine by the adrenal medullae during exercise, as a result of sympathetic stimulation directly activate hormone-sensitive triglyceride lipase, which is present in abundance in the fat cells, and this causes rapid breakdown of triglycerides and mobilisation of fatty acids.
In anorexic patients, they have an increased level of cortisol. When normal quantities of carbohydrates are not available to the cells, the adenohypophysis (anterior pituitary), for reasons not completely understood, begins to secrete increased quantities of the hormone corticotropin. This stimulates the adrenal cortex to produce large quantities of glucocorticoid hormones, especially cortisol. In turn, cortisol mobilizes proteins from essentially all cells of the body, making these available in the form of amino acids in the body fluids. A high proportion of these immediately become deaminated in the liver and provide ideal substrates for conversion into glucose.
This should be more relevant as opposed to pathophysiology of weight loss
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