What kind of fat is that? (2/3/12)
Fat. The word sounds simple.
Once upon a time, fat biologically was simple. Fat cells supplied living storage energy. Their round, white globular forms sat by silently ready to power cellular function – especially when hard to store glucose was not available.
Fats were also employed for innumerable non-power uses – including the critical, information passing lining of cells and the essential, speedy transport of nerve cell electricity – 60% of your brain is fat. But human fat cells remained unpopular. They might stick in your skin, making for unfashionable cellulite; flock around your belly’s vital organs, making for unsightly belly fat; or help produce bigger but not necessarily prettier breasts and backsides. And the big, white fat cells making for this all unbeauty was simultaneously physiologically dull and boring.
The Changing Face of Fat
Here are a few developments in the life of fat from just the past few years:
1. Fat cells are major endocrine glands.
That’s right, fat cells make hordes of hormones. They include leptin, the appetite suppressing hormone that was supposed to end the obesity epidemic – and didn’t; adiponectin, with wild, widespread effects on how fat is deployed; resistin, which modulates many things including insulin resistance, one of the banes of obese people everywhere; tumor necrosis factor alpha and other inflammatory substances.
Fat the hormone is particularly common around abdominal organs. Belly fat is bad for you in ways researchers have just begun to tackle.
2. Adult humans have brown fat.
Brown fat is what keeps hibernating bears alive. By liberating much more heat more quickly than white fat – brown fat is brown because of its extra energy making mitochondria – it keeps bears functioning in winter.
Brown fat does the same for human infants. Babies can’t shiver. Brown fat keeps them warm – and alive.
Then brown fat disappears – or so people thought.
A few years ago brown fat was found in human adults – if they were thin and kept chilled. Only then did brown fat show up on physiologic scans.
Immediately the idea came out – is brown fat one way to thinness?
3. There’s more than one kind of brown fat.
The kind found in rodents, thickly applied, seems to originate from muscle cells.
But mice can be made to turn their white fat into a different sort of brown fat – through exercise. And this fat is thinly and irregularly applied throughout tissues.
As I’ve written, changing white fat to brown fat is a much bigger trick than converting brown eyes to blue eyes. And you can do it just through physical activity.
This recent work, by Bruce Spiegelman and colleagues at Dana-Farber, demonstrates brown fat engaged in varieties of physiologic resurgence – but so far, no particular weight loss when you convert white fat to brown.
4. Take out brown fat and bones get brittle. In studies at Tufts, Clifford Rosen has looked at mice who cannot make brown fat.
One result – terrible osteoporosis. Brown fat cells may be required for normal bone health.
Fat and fat cells are critical to life. Like most cellular systems, they’re amazingly complex and interlinked.
Fat is cell linings and fuel. Fat is white and brown and mixed. Fat is an endocrine gland that can help cause heart disease and diabetes. Fat cells can be transformed in form and function into cells that may help control weight, diabetes, and bone health by simple exercise.
We can change the forms of fat just by our own will.
So it is true – fat is beautiful.
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