The fitness craze has been around so long, that it's not entirely accurate to even call it a "craze". It's more of an innate human desire to become more attractive and physically healthy. Unfortunately, it's also an innate human desire to take the easy way out and want instant gratification. Thus, instead of putting on those tennis shoes and jogging at the crack of dawn, we are much more apt to shell out $9.99 for some idiotic contraption on the Home Shopping Network that promises quick and easy results.
This combination of traits has made us extremely vulnerable to charlatans and frauds.
I find it interesting to look at the fitness section of my old catalogs. The odd contraptions being sold through JC Penney, Sears and Montgomery Wards were painfully awful. It's certainly no better today, but some of the stuff being sold was just ludicrous..... case in point, the "air jeans".