Your body has billions of fat cells. (For example, people with healthy, normal weight carry around some 40 billion fat cells.) Each one is a miniature reservoir for storing fat. Fat cells work in a rather unusual way. When your body squirrels away fat, your fat cells don’t do what you might expect them to—multiply. Instead, they gobble up the extra fat, inflating themselves like rubber balloons. In fact, if you take a close-up look at a fat cell under a microscope, you find that nearly the entire cell is filled with a greasy droplet of fat. The rest of the cell—the cellular machinery that runs the shop—is squeezed to the very edge of the cell, and much more difficult to spot. Early researchers wondered if fat cells actually did any work on their own, or if their squashed functional parts were completely disabled.
Fat cells make up a spongy type of tissue that biologists call adipose tissue. Inside this tissue, your body packs fat cells together in a neat, almost honeycombed pattern. It’s like bubble wrap for your body.
In the past, scientists thought fat cells were simply boring blobs of lard. We now know that they don’t hang around idly—instead, they release massive quantities of hormones that have effects throughout your body. For this reason, many fat scientists (er, make that scientists studying fat) argue that fat isn’t just excess tissue—it’s a smart and powerful organ in its own right.
At this point, it’s natural to ask what these fat-secreted hormones are up to. Although the interaction between fat cells and the rest of your body is fantastically complex, here are some key examples:
• Female fertility. As women know, carrying and delivering a baby is a body-straining odyssey. Without a bare minimum of fat, your body won’t even let you try. If your body decides that you don’t have the necessary fat reserves to live through a pregnancy and nourish a baby, you’ll stop menstruating. Regain the fat, and the deal’s back on.
• Appetite. Fat cells release a hormone called leptin that tells your brain to damp down feelings of hunger. Leptin is often blamed for the nearly inevitable weight gain that follows severe dieting. As you lose fat, your leptin level falls and your brain feels less satisfied, becoming much more likely to trigger a late-night cheesecake craving.
• Regulating the immune system. Fat cells release compounds that fire up parts of your immune system. Too much fat, and these signals get amplified to harmful levels, triggering inflammation deep inside your body. This inflammation can damage your body and lead to other conditions, like heart disease, arthritis, and type 2 diabetes. On the other hand, elite athletes who eat an extremely low-fat diet—say, ultra-marathon runners—end up suppressing their immune systems and becoming more susceptible to infection.
Hormones are special chemicals the body uses to send messages from one place to another. Your fat releases hormones into your blood, where it can travel to other body parts, like your brain.
It might seem that a little extra leptin would make a great diet pill. Unfortunately, it doesn’t work that way. The problem is that your body is far more interested in preventing starvation than in fighting weight gain. If your leptin level rises, your brain adapts to this new level and considers it the “new normal.” Then, when you stop taking the pills and your leptin level falls, hunger quickly sets in. This process, like much of the body’s appetite-control system, is a bit biased. In fact, it looks a lot like a one-way street to more eating.
Source of Information : Oreilly - Your Body Missing Manual (08-2009)