Obesity is probably decreasing in the USA. What changed (in 1998) was to change the definition of obesity down to 30 lbs. overweight, thus adding millions to the "obese" column.
There's no way somebody 30 lbs overweight (by whatever standard is used) is what people consider obese. 30 lbs overweight is "plump," pudgy," or, as they used to say, "sleek" or "prosperous-looking." In women, "matronly."
In fact, being 30 lbs overweight has no ill medical effects at all. The aesthetics of it are, of course, highly subjective.