Fit isn't a shape. It is a description of capability. It isn't necesarily healthy. You can be fit to play football, fit to climb a mountain or fit for a game of scrabble or fit for bed. Being fit for one element is not fit for another as different body and mind preparations are required.
A pair of jeans may fit your body but not your image.
A car might fit your lifestyle, or image but not your budget. It is about compatability it is not about shape.
A fit body does not have a specific shape. We train to make our bodies to be compatable with what we wish it to accomplish. This will result in different functional shapes that depend on many factors.
This pic from dyemelikeasunset.deviantart.com
A fit body is compatible with the demands of your life. Some of these demands can be extreme. You may wish to lift heavy weights, you may wish to cycle very long distances. These events will put a strain on your body that pulls it out of healthy balanced state and causes pain. That is not healthy but it is still fit for a particular purpose.
A healthy body will be able to cope with all normal human tasks and range of motion without breakdown and it will be without pain or disease. It will be a good place to enjoy life and it doesn't have a particular shape.
I like to tell my clients that in any society there had to be a guy who chased the deer and another to carry it home. There was one who climbed the cliffs and one who roamed for hours collecting fruits and herbs. All are valuable but they all have to be in their own particular shape.