Strong jawline is definitely a coveted feature in our present culture. It evokes a look of power, strength, and confidence in men and women, which is what many of the best supermodels express
The change in lower jaw width is very significant. A one kilogram change in weight is too small of a variation to produce such a big visual difference.
We love faces with strong, square jaw bones and hollow cheeks because they emanate self-confidence and look more interesting. We ourselves also feel more secure when we feel pretty.