Last week Britain banned a Saint Laurent ad for featuring an "unhealthily underweight model". The black-and-white magazine ad apparently breached a code of the UK's Advertising Standards Authority (ASA) and was subsequently pulled. Saint Laurent was given a slap on the wrist, and told not to repeat its mistake, while The Guardian reported the following statement from the ASA: "The ASA considered that the model's pose and the particular lighting effect in the ad drew particular focus to the model's chest, where her rib cage was visible and appeared prominent, and to her legs, where her thighs and knees appeared a similar width, and which looked very thin, particularly in light of her positioning and the contrast between the narrowness of her legs and her platform shoes. We therefore considered that the model appeared unhealthily underweight in the image and concluded that the ad was irresponsible." The ad, published in Elle magazine, shows 18-year-old Dutch model Kiki Willems lying on the floor in a short dress, heels, sheer tights and cropped jacket. Does she look underweight? Yes, in the picture (right) she does. But is she is skinniest model I've seen in ads or editorials? Not by a long shot. But as the online debate has many Twitter users lauding ASA's decision, we have to acknowledge there are shades of grey to this issue. For highly produced fashion images, Photoshopping is de rigueur - and here the high contrast effect and lighting of the photo adds significant thinning. Different poses can also amplify the effect. Might all these make a healthy yet naturally skinny girl look unhealthy? Yes, it could. But people can also take the view that what this model looks like in real life and natural light is beside the point - with fashion constantly promoting unhealthy, and unattainably thin bodies, perception rather than reality is key. The effect on young girls' and women's body image is no doubt significant. The fashion industry will always struggle with balancing its inherently aspirational nature with some semblance of public responsibility. Although fashion will always seek out extremes of whatever is perceived as "beautiful" in a culture and era, the current state of affairs is unsustainable. High fashion samples are now tiny, and apart from teenagers, most models work hard and eat very little to maintain such a thin physique. The most recent significant change came in the mid-1990s. The rise of grunge and androgyny overtook the body ideals that supermodels such as Naomi Campbell, Cindy Crawford, Christy Turlington or Elle MacPherson represented. Young waifs have been "in" ever since. But there is a backlash, and the sports lifestyle trend has reintroduced another image of the ideal to women - which has now gone mainstream. Governments are also getting involved in an attempt to turn the tide. France banned the use of "unhealthily thin" models this year; although details on how this is judged and implemented remain fuzzy. In 2012, Vogue moved to "ban" models who were too skinny and/or underage from its pages, but again this has been difficult to impose objectively. In Asia, we are way behind in opening up a dialogue on this issue. You have to laugh at the ridiculous slimming and beauty ads in the MTR when you think of how an organisation such as ASA would regard them. This issue isn't going away soon and that is a good thing. As its cultural clout grows, fashion's most pressing issues will continue to be sustainability and social responsibility. The water is murky, but we all must wade in.