|
|
|
| Current Issue |
|
|
| Resources |
|
|
|
The Wild Side of Fat
| Article
# : |
18733 |
|
|
Section : |
NATURAL SCIENCE
|
| Issue
Date : |
8 / 1991 |
2,968 Words |
| Author
: |
Caroline M. Pond
Caroline M. Pond is senior lecturer in biology at the Open
University in Milton Keynes, England, and writes on general
biology, evolution, and physiology. |
No living matter gets more consistently bad press than fat, but we vertebrate animals can't live without it, particularly if we eat a fatty diet. Fats and oils are poisonous to tissues such as the heart and the brain if their concentration in the blood is too high; the biochemically tricky job of handling such a dangerous fuel is performed mainly by a highly specialized part of the body known to biologists as white adipose tissue, and to cooks and butchers as "fat." Spare a thought for poor old adipose tissue--despised by fashion magazines, excised by cooks, condemned by nutritionists, and ignored by biologists. Everyone wants to reduce it, to make it grow somewhere other than where it normally grows, or simply pretend that it isn't really there. Anatomically homeless and physiologically underrated, white adipose tissue is widely regarded as an interloper; at best insignificant and dispensable, at worst a sinister intruder and perverter of normal metabolism. It generally receives only brief mention in biology courses, which often imply that its presence in large quantities is somehow unnatural.
Obese--naturally
There's nothing wrong with having lots of adipose tissue: Many of the animals successfully living in the harshest conditions are obese, at least for part of the year. Highly seasonal environments such as desert and polar regions are promising places to look for such "professional" fatties. On Svalbard, an archipelago about 700 miles north of the Arctic Circle, the lowlands are snow-free for less than four months of the year, and the native reindeer do most of their eating during this brief period. At other times of the year, they have to dig through the snow to reach dried plants beneath. Such foraging becomes harder and harder work, eventually not worth the meager rewards that it yields. The reindeer become fat in the autumn and early winter; the adipose tissue becomes more active, and its capacity to take up nutrients from the blood and lay down fat increases. As winter sets in and the days shorten into continuous night, the reindeer's appetite declines. They eat less, even if offered abundant food. They may be very thin by the time the spring restores their appetite--and enables plants to grow once more.
Although they inhabit many of the same areas as reindeer, polar bears have the opposite cycle of feasting and fasting. They feed almost exclusively on seals, usually catching them as the seals surface to breathe through holes in the ice. Hunting is most successful when the sea is almost completely frozen over, with only a few breathing holes remaining. From late June until the sea freezes in October, polar
...
Read Full Article
Look for this article in Ask.com
|
|
