In 1970, Jones established Nautilus Sports/Medical Industries. As of 1984, there were over 3,000 Nautilus Fitness Centers (each of which had to have at least 12 Nautilus machines to use the name), plus numerous other machines in training rooms, colleges, high schools and professional sports teams. Since then, other machines such as Cybex and Paramount have been developed to help isolate and work individual muscle groups. the rest of article

The effect of this has been noticeable. The "hot" bodies shown in movies half a century ago would be laughed at in today's rippling "cut" or "buff" images. Even Barry pointed out that George Reeves, in his Superman suit in the 1950's TV series, had a noticeable potbelly, and not the "six-pack" required for any actor playing that role today.

With the explosion of cheap clothing made available by the Industrial Revolution, it is hard today to tell social status. Most people can't tell a Paris original from a K-Mart's rip-off, and thus the effect of wearing the best clothes is lost on average viewer. Thus to some extent, the body itself is becoming the fashion statement - tan, muscles, hair length and color, tattoos, and pierced body parts.

Thus the connection between being fit and what was considered an ideal body shape is of fairly recent times. There are people today who take working out and in particular, losing weight, to unhealthy extremes, because they suffer from a poor body image. This is in the same vein that Victorian ladies laced their corsets up so tight they displaced their internal organs.
Corset-Sears-1908

The other thing to consider is that fitness is a science still in its infancy. If it seems like every couple of months they changed their ideas, they do! Back when I was in school, gym teachers told you NOT to drink water when you exercised on a hot day, as they claimed it would give you cramps. Instead they gave out salt tablets. (It's a wonder any of us survived.)