送交者: xj 于 2006-3-20, 13:09:26:
回答: Interesting. I' m curious about this. I have 3 questions for you. 由 Enlighten 于 2006-3-20, 12:42:01:
stomach is included in the waist. :-)
More strictly speaking, when we talk about fat deposit, we should distinguish subcutaneous fat (under the skin) and visceral fat (deep inside fat) around waist. These can be measured by CT or MRI.
In asians, studies have found that there is a disproportional higher visceral/subcutaneous fat ratio than those caucasians do. That is, caucasians not only put a lot of weight on their waist, but also put weight on elsewhere like back and butt.
The detrimental effects of a large visceral fat are hypothetical but some are supported by biological experiments. For example, the adipocytes (fat cells) in visceral fat are more metabolically active than subcutaneous fat, and there are more blood vessels around them too. visceral fat deposit is more mobile than subcutaneous fat, so the free fatty acids are more likely move in and out of visceral fat, thus causing a heavier load on insulin and liver. The signalling sent out by these adipocytes are generally not good (in modern human body) because most of them are asking for more energy expenditure to use fat, thus causing all disturbance in human body. We just can't use up all these extra energy!
fat cells are not passive storage box, they are regulators.
In terms of evolutional stress. That is my guess. I think Chinese have been in agriculture for too long. Agriculture causes steady increase of population, but on the other hand make people in constant semi-hunger. The average energy intake among ancient chinese are lower than those in caucasians because Chinese emphasize on vegatable foods rather that animal products. This lower energy intake may selectively create a gene profile which is too thrift.
It could be the other way around. For example, because Chinese live in agriculture society so there is no need to worry too much about foods because there will be foods available in forseeable future (within months). So Chinese didn't develop a tendency to deposit energy for long term (such as in subcutaneous fat), instead,energy stays in tummy so it is readily to use. Maybe storing fat in tummy is evolutionally earlier than storing fat in back and butt. :-) So Chinese may experience less evolution stress.