I understand that this is a very controversial issue and my personal take on this is not going to be thrilling for the "gym girls" or for the "fat-ivists".
I have read many manifestos concerning "Fat Pride" and discussions about the fat pride movement. I understand railing against the mainstream beauty paradigm. However, telling people they are not damming their health by avoiding exercise is wrong. That having a doctor tell you that your weight and lack of healthy diet and exercise is causing problems is judgmental.Being over-weight can severely impact your health. Having gone from 125lbs to 220lbs (yes, I was pregnant), I can tell you what a difference extraneous weight makes. My joints ached constantly, they still do even 6 months after being pregnant. I couldn't move properly, I couldn't bend. I could not engage in the activities I enjoyed. Walking became difficult. The problem is not the form, it's the function. Can you live a healthy lifestyle? Can you do what you enjoy doing? Can you fit comfortably in public spaces?
The problem is not that we should be encouraging people to become proud of being grotesquely large. It's that what we now consider "fat" is not actually fat. I was watching the movie Brand and one of the characters came up with an absolutely diabolical plot. They were going to start marketing things with Fat being beautiful! Oh, my gosh! In fact, he made a comment that it would be the biggest coup in history, that they would use marketing to change how humans viewed beauty!!!! 
Utter nonsense. This has been going on forever.
If you look through history, even just the last two thousand years, the female shape has changed to suit whatever was selling. The one thing that was almost universal was that the only times androgynous or overly-thin silhouettes became in-style would be during or directly after times of war or famine. Otherwise, whether we are talking the ancient Greeks, the Greek revivalists, the Rubenesque women of portraiture, even the tightly-corseted Victorians, women were characterized by their curves.
The more meat on a woman, the better her resources, and the more likely she is to produce healthy children. 
Fashion has followed; during the renaissance, women wore "bum rolls" (fabric worn tied around their hips to accentuate the difference between their waists and their hips), not to mention petticoats, farthing gales, etc. The first major emergence of the boyish figure was during and directly after WWI. If you were poor, you were restricted by extreme rationing. If you were wealthier, the best way to appear patriotic was to mimic the slimmer figures of those under strict rationing.
After WWII began to help alleviate some of the Depression-era poverty of America, the attractive female returned to her slim-waisted but hour-glass shape. 
As women entered the work force during the 1960's, the ideal shape began to masculinize once more. Not only did de-emphasizing one's female shape hopefully help one become recognized as closer to equal in the career world, but women were gaining new rights which had previously been reserved only for men. They were able to control their reproduction and were socially more likely to have control over their sexual choices. Men could no longer use their normal methods of control over women. What they could do was infantalize them through raising pre-pubescent girlhood to the height of sexual attractiveness. Twiggy became a fashion icon; the eternal girl with immature or nonexistent curves. With the rise of thinness as the epitome of chic, fashion designers were blessed. No longer would they have to create clothing that looked well-tailored to the widely-differing female form! No more would they be slaves to the curves! They could design clothes based on how they wanted the clothes to look; not how they would look *on* a person. The models were no more than hangers.
Unfortunately, those with free time to exercise or the money to eat the now much more expensive healthy, natural food were able to keep up- they began to thin themselves down to match the fashions. As with all fashion, it began to trickle down. If you did not have the time to work out or the cash to eat well, one could always starve themselves. As the lower classes became smaller, the highest echelons had no alternative but to become even smaller. If you compare ads from the 1990s (marked by extreme slightness) to those of today, you are faced with the realization that what was previously both thin and fit is now too large. Those that are touted as "gym girls" are very rarely in shape.. they are thin. 
They do not have powerful thighs for running or pushing weight; they have tiny thighs that do not touch. This is supposed to be our ideal.
If you take a look at clothing in everyday stores, the clothes are constructed for straight or almost stick-thin silhouettes. Those shirts that are attractive at a size 0-4 are the same shape as those at size 16-18. Neither of those shirts previously mentioned accommodate breasts of average size. When I graduated high school, I was a size xs or s (there was no xxs), and had A-cup breasts. A few months later, I had C-cup breasts. My was it size had not changed but I was now a medium or even large in shirts and dresses. When I began wearing bras, the smallest that were available were A cups and the enormous, ridiculous breasts were DD-cups. Now, there are AA and AAA cup bras and my "enormous" postpartum breasts are H cups. The most popular stores rarely carry anything larger than a C-cup bra.
Our thin is now terrifying. I do not know a single woman that can eat a dessert and enjoy it; they will almost always think about their physique before digging in. Our jeans would not look baggy on those that were rescued from concentration camps. high fashion jeans are rarely offered over a size 26 and have been known to go down to size 18 (that's inches. an 18 inch waist was considered unreal in the days of corsets... and those jeans are not measured at the natural waist). Do you think I'm exaggerating? Look at this woman:
Versus:
Or this:
Think these may be exceptions, check out this story:
http://www.dailymail.co.uk/femail/article-1279766/Former-Cosmo-editor-LEAH-HARDY-airbrushing-skinny-models-look-healthy-big-fat-dangerous-lie.html
And that was in 2010, 3 years before now when we're in the height of the jeggings craze.
As someone that has always had an hour-glass shape in a stick-figure world, things can be frustrating. Whether I am at 180 (48-36-46, 7 weeks postpartum) or at 100 (30-22-30), I never have less than an 8 inch difference between my waist and my hips. This has always made finding clothing extremely difficult. When I was skating, my thighs were too big for girls jeans. Even if I wanted to go androgynous, I couldn't... binding my chest would not hide the obvious flares of my ribs and pelvis. When I was at 115lbs and climbing regularly, I could fit into Hollister size 2-4 jeans but my calves were too muscular (yay advent of skinny jeans, huh?). I was thrilled when I noticed that some 1930's-1940's styles were coming back into style this spring! I was psyched!!! Then I tried them on and realized that though there was a "waist", the dress I tried on was still cut along a straight line. They all were. Now we're redesigning clothing meant to fit the female form for something closer to a 9 year old girl's. Every grown woman is being taught to be ashamed of her body.
We need to get back to a healthy middle. We need to find balance, and create a society that lauds (and produces clothing for) all different shapes and sizes.
