I think you're arguing against a straw man here - as far as I can see, no one here is advocating putting overweight and unhealthy people in product ads. This is more about the cases where star designers fire models who are 5"8' and weigh 120lbs because they are deemed "too fat", while the photoshopped final picture looks like this:
Given your biography it's quite understandable that you attach a certain importance to a healthy diet. However, there is no way you can look like that on any healthy diet. I don't think it's healthy for young girls to make this their ideal of physical beauty either. I have a hard time seeing any natural beauty in hips that are narrower than the head, but you find models engaging in dietary practices that are actually quite unhealthy just to adhere to this standard. Obsessing about things tends to be bad.
The natural sex drive may make it natural to favour aesthetically beautiful people, but please don't forget that values of beauty are largely culturally communicated. In fact this is why we have this discussion in the first place. I think it's quite appropriate to point out that something is wrong with the image of female beauty as communicated, for example, in Western fashion media at the moment - we've come to the point, in fact, where even the Western fashion media have realized that. Cancer, diabetes, heart diesease and osteoporosis (to take your examples) may be higher than ever in history, but, one can't help noticing that, for example, bulimia and anorexia nervosa are also more widespread than ever. Those have nothing to do with natural sex drive and the 'correct' female body in terms of physical health, but everything with a distorted image of the self and a self-obliterating drive to conform with a wildly unnatural ideal of the body, and you don't have to be an advocate overweight models to notice that.