Everyone knows that being fat is bad for you, but most people can’t explain exactly why. Some reasons are obvious. Fat tends to go hand in hand with diabetes, and more weight means increased stress on joints and the heart. More puzzling to researchers is that excess fat seems to be linked with cancer of the kidneys, colon, and liver, and even to cognitive decline.
Until fairly recently, fat was thought to be inert, evolution’s wobbly way of letting humans store energy for lean times. And we’ve long known that it’s better to be slightly overweight than underweight, as a recent study in the Journal of the American Medical Association reiterates.
Starting in the 1990s, though, scientists began to realize that fat is best understood as a single huge endocrine gland, one that wields powerful influence over the rest of the body.