Initiating Eating

Low levels of circulating glucose (and a corresponding higher rate of glycogen to glucose conversion) are important in the initiation of eating. Experimental manipulations that decrease glucose availability are a powerful means of stimulating eating (7). It is important to note, however, that a low level of circulating glucose is not an entirely accurate characterization of the metabolic trigger for eating. Consider untreated diabetics, who have a high level of circulating glucose but who are chronically hungry, because the glucose is not metabolically available owing to insufficient insulin, the hormone necessary for glucose uptake into cells. Thus, it is the unavailability of glucose that is the critical signal. Accordingly, because of its importance in clearing glucose from the bloodstream, insulin is considered an important hormone for the initiation of eating.

Recent research attempting to characterize more precisely the connection between blood glucose level and feeding indicates that meal onsets are preceded by small transient declines in blood glucose (8). If this decline in blood glucose is prevented, feeding will not occur. Feeding will not begin until a transient decline in blood glucose is experienced, supporting the notion that a drop in glucose availability is causally related to eating. Of special interest is the finding that the glucose-drop signal that initiates eating is of surprisingly short duration and small magnitude.

Whereas glucose appears to be important for regulating eating in the short term (ie, meal to meal), lipids appear to play a more important role in regulating food intake in the long term (9). During fasting, the body's fat reserves are converted to fatty acids for energy; this process probably provides an additional signal for turning on eating.

Diabetes 2

Diabetes 2

Diabetes is a disease that affects the way your body uses food. Normally, your body converts sugars, starches and other foods into a form of sugar called glucose. Your body uses glucose for fuel. The cells receive the glucose through the bloodstream. They then use insulin a hormone made by the pancreas to absorb the glucose, convert it into energy, and either use it or store it for later use. Learn more...

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