Saddlebags, spare tires, muffin tops we've dreamed up as many names for body fat as Starbucks has for coffee. Even as otherwise sensible, well-adjusted adults, many of us spend a huge amount of time dwelling on our double chins, chubby ankles, or flabby arms. We're both fixated and repulsed: We hate our fat, but we can't stop thinking about it.
Well, stop obsessing about your love handles for a minute and ruminate on this: your fat doesn't just sit there glob-like and idle. Fat is actually a great big gland, churning out hormones and other chemical substances that are essential to many bodily functions. Depending on where it's located, fat may protect you from developing heart disease, high blood pressure, and diabetes. Much of this research is just emerging, but when you've heard the latest, you'll never look at that little pooch over your waistband the same way again.
Basically, fat is stored energy. When you eat, your body transforms carbohydrates, protein, and dietary fat into fatty acids (chains of molecules that are the building blocks of body fat), glucose (blood sugar), or amino acids. These provide energy that you either burn right away or pack up for later. Without body fat, you'd have to eat all the time just to keep your body functioning, your heart beating, your eyes moving across the page, and your hand traveling to your mouth to sip your latte.
Fat that isn't used right away gets stored in cells. If you looked at one of them under a microscope, you'd see standard cell equipment — a nucleus, mitochondria, that sort of thing dwarfed by a big fat droplet that makes up about 85 percent of the cell's volume. Fat cells typically start at 5 millionths of a meter in diameter, too tiny to be seen by the naked eye. But they're insanely elastic. each one can increase by 100 times in volume, to about the size of the period at the end of this sentence — if you keep stuffing pizza down your throat. For a cell, that's positively ginormous. For the longest time researchers thought that fat cells were kind of like height: you kept adding to them until you passed puberty, then stopped. But a 2004 study published in the American Journal of Physiology: Endocrinology and Metabolism found that people actually create new fat cells throughout their adult lives. When a fat cell is full to bursting (i.e., period size), it sends a chemical signal to surrounding tissue to create new ones. While an average nonoverweight adult has roughly 30 to 40 billion fat cells, someone who's very obese might have as many as 100 billion. And once you've got a fat cell, there's no way to get rid of it — even by losing weight — unless you suck it out.