Hi Ed

Thanks for your query and the interesting points it raises.

Fat has always been focussed on as a dietary enemy because the saturated kind in particular raises cholesterol. And in that sense it is stil the main one to watch. But a sugar-laden diet and in particular a high glycaemic index diet is also a potential; concern. Studies seem to indicate that if two people reduce their calories by the same amount , the person  eating a low glycaemic index diet will lose slightly more weight than the one eating a high glycaemic index diet . High glycaemic index / sugar diets are also liked with diabetes and heart disease and there's a  tie in with syndrome X, featuring  an overweightapple shape, high blood pressure and /or cholesterol and insulin resistance. 

Women in particular react badly to a high sugar diet - high sugar raises blood  triglycerides - a heart disease risk factor  - in women but not in men it seems.

One thing is important to remember though, - although sugar can easily be converted to fat, this will only happen if the calories you eat in total are surplus to requirements. At the end of the day, calories are still king and you only  lay down fat if you have more than you need.

Your other issues is regarding fructose, and you are right that this is a sugar that seems particularly bad in large amounts. Ironically it is the sugar found naturally occurring in fruit, but experts say that we should never worry about the fructose in fruit because fruit has so many other things going for it, like fibre,  vitamins and antioxidants, Large quantities of fruit juice can pile too much fructose into your diet though as you point out, and this can be as bad  as having fizzy drinks sweetened with high fructose corn syrup. I recently wrote a couple of articles on fructose - if you private message me I am happy to send you the copy for you to read.