You are perhaps more optimistic or openminded than what would be expected of the average person, based on these comments, CL. Some things are better left in secret, and not discussed in the fashion you suggest, particularly between couples. Love between couples goes through phases in their relationship as time progresses. Sometimes it grows, sometimes it remains the same, but sometimes it dimishes greatly, as shown by the number of divorces and separations, as well as those still married, but unhappily so.
If a couple has been married for a long period of time, there are going to be physical changes that occur to each, that make them have their own self-doubts when they look in the mirror. It's human nature for people to be more critical of themselves and to think their "flaws" are more glaring than they likely are to others.
One would hope that the love between the couples would survive those cosmetic changes. But sometimes it doesn't. And other times, even though the love survives, it is unkind to make the other partner aware that the fantasies that a person harbors are about someone vastly different than their spouse. For example, if a couple gets married, and she is a size 5 at the time, and he is whatever is the equivalent for a man, at some point, they may both have gained a great deal of weight. Suddenly she is a 2X, or a 20, and he has Dunlops Disease (his belly done lopped over his belt).
It is probably more amusing to the man to find out his wife lusts after Brad Pitt, than harmful. But for the woman to find out that the man is having lustful thoughts about women on TV and at home and or at work, who are the size she USED to be, and likely never wlll be again, is usually hurtful. Also, she knows she cannot compete with younger women, even if she lost the weight, since there is only so much you can do to stem the tide of aging, if his fancy involves younger women. The same would likely be true if the man has his own isues with balding, for example, and the wife is enamored of Antonio Banderas or Fabio. It would be even worse, if he found out that her appreciation for men with lots of hair, relates to someone she knows and sees frequently at home or at work.
Sometimes the kindest thing, if you love someone, is to not share all your thoughts, particularly if those thoughts would hurt them. Listen to Carley Simon's song "We Have No Secrets," sometime, and you will see how she explains it. Here are the lyrics: http://www.lyricsdepot.com/carly-simon/we-have-no-secrets.html