Vegetables and rice are full of carbohydrates, fruits are indeed full of sugar - and carbohydrates (well the ones we can digest, anyway) are broken down into simple sugars exactly the same as table sugar. Table sugar (sucrose) is a 2-molecule compound made up from glucose and fructose - fruit sugar is mainly fructose (as is honey), and starches and complex carbohydrates break down to glucose.
The more carbs you eat, then, the more "sugar" you are putting into your body, even though it doesn't start off as being actual sugar.
Research is also usually funded. Very little of it is done without funding, and therefore the funders often have an agenda for the outcome that they expect from the research. Not saying that they're exactly falsifying data, just that they do the stats, and design the protocols, to skew the results in the direction they would like. Not ALL research is done this way, but a fair amount is.
Re. the fats thing - I watched a documentary on the TV (and OH how I wish I'd video'd it!!) back in the 1980s that suggested there was a report done into the causes of heart disease in the early 1970s, and that initially 4 dietary factors were identified - high salt, saturated fat, cholesterol and sugar. But, according to this documentary, lobbying from the Tate family manage to get the sugar part of this report removed (big supporters of the Govt, lots of clout) which left us with salt, sat. fat and cholesterol.
The dietary cholesterol thing was the first to be debunked, when it was realised that we make 80%+ of our own cholesterol, and conserve it quite highly (i.e. reabsorb it) - dietary cholesterol has very little effect on overall cholesterol levels, it's an internal biochemistry issue that causes increases in cholesterol. Then came the subdivision of cholesterol into "good" and "bad" - neither being true, both are essential - and the ratio being more important, then add in the triglycerides (fatty acids) and it became clear that it was a much more complex picture than just "stop eating eggs and prawns".
It has now been realised that all this high-sugar, high-carb, low fat food we've been led towards has in fact increased the obesity rate; excess sugar/carb in your diet leading to it being laid down as fat once the body has reached its limit of carb storage, and leading to insulin resistance and then type II diabetes.
You could say that vested interests are entirely to blame; or you could say that it's new learning that comes out that changes our beliefs, or changes the "facts" as we know them; or a combination of the two.
I used to get information from the coffee council quite regularly, on how caffeine/coffee was shown to be good for you in various conditions - beneficial for diabetes, cancer, you name it. And then at the same time there would be conflicting research coming out explaining how caffeine exacerbated diabetes and could be damaging in other health conditions - leaving you with a face like 
and wondering whether the good outweighed the bad in a cup of coffee!
But I have to say that I tend to "follow the money" when I see conflicting research - look at who has done it, who has funded it, conflicts of interest etc.
Something else entertaining - several years ago, the New England Journal of Medicine (NEJM) decided that they wouldn't take any papers where money had exchanged hands between the primary researchers and the people who wrote up the paper (a common practice) - they apparently didn't get enough papers to publish! So they had to revise their restriction to "only taking papers where there was an upper limit on how much the authors had been paid" (not sure how much that was).