I'm far from being a strident feminist, but I do feel that bloody double-standards is alive-and-kicking in the work-place!!
Since when have men ever lost a wink of sleep over hair colour, eye-brows, nails etc?
I bristled when I read your words, floppity
*it's a professional job in which slightly overweight middle-aged / old men tend to dominate" - I bet they don't worry to the extent you are (sorry to point that out!)
Unfortunately the likelihood of your manager being honest with you and saying there are issues with your appearance are zilch I'm afraid - they'll give a hundred and one reasons why they can't promote you, or get you involved in more exciting projects etc, but none of them will be related to appearance.
So I would say, do the best with what you've got, don't sweat the small stuff (no pun intended!!), keep those skills up to date and KOKO in 2016
As an aside, I read in a recent Times article that being too attractive can hold a woman back [irony icon] - women who are reasonably well-presented, suitably dressed, coupled with great (differentiated) skills are most likely to get the best jobs, not someone with excessively stunning looks. It gives me hope, ha-ha!