Since 1993, most packaged food sold in the U.S. has been required to include a "Nutrition Facts" label that lists the amount of fat, cholesterol, sodium, protein, carbohydrates, fiber and sugar in a serving and that includes some information on recommended daily intakes.

During that same period, Americans' diets have gotten worse — their waistlines have expanded and public-health problems related to poor nutrition have grown. I'm not going to blame the Food and Drug Administration's nutrition-labeling rules for this state of affairs. But they don't seem to have helped a lot, either.

Now the FDA is overhauling the Nutrition Facts label. Last year, it proposed several changes to the look and content of the label, among them a reality check on serving sizes and a disclosure of how much sugar has been added to a product. Last week, it added another wrinkle — foodmakers will have to report the percentage of the recommended daily intake of added sugar that's contained in a serving.

Paying more attention to sugar makes sense. A growing body of research shows that it — and not fat and cholesterol, the earlier targets of dietary strictures — is perhaps the nation's public health enemy No. 1. But the way the FDA is going about it is weird — and confusing.

The issue is that the agency is targeting only added sugar. But sugar is sugar — the kind that occurs naturally in orange juice isn't intrinsically healthier than sugar added to a soft drink (or to cranberry juice, which is unpalatable without added sugar).

The reason for the focus on added sugar becomes a little clearer when one peruses the Scientific Report of the 2015 Dietary Guidelines Advisory Committee. This 571-page tome was released in January and is meant to inform the once-in-five years update of the dietary guidelines from the U.S. Department of Agriculture and the Department of Health and Human Services that is due out later this year.

There is much discussion in this advisory report of "empty calories" — calories that come from foods that don't provide much else in the way of nutrition. Soft drinks and sweets are major sources of these empty calories, and they have lots of added sugar. Therefore added sugars have become a major target of public-health research and advocacy. Of the studies that the advisory committee cites on sugar's dangers, most measured added sugar and not overall sugar consumption.

In context, this makes sense. Fresh fruit and fruit juice may contain lots of natural sugar, but they have other nutrients, too, and they comprise a pretty small share (4.5 percent in 2009 and 2010) of Americans' overall caloric intake. So why focus a lot of attention on them?

When it comes to communicating nutritional information to the public, though, the emphasis on added sugars seems less than helpful. A study to be published soon in the Journal of the Academy of Nutrition and Dietetics found that consumers had more trouble judging products' sugar content when the added sugar information was included. This study was funded by a food industry group, but the FDA's own research appears to at least partly back up this conclusion.

Including the percentage of recommended daily intake of added sugar seems to be an attempt to make things a little clearer. As Susan Mayne, director of the FDA's Center for Food Safety and Applied Nutrition, put it in a recent blog post:

"For example, a consumer who drinks a 20-ounce sugared beverage may be surprised to know it contains about 66 grams of added sugar, which would be listed on the label as 132 percent of the Daily Value."

But the idea of a daily recommended intake of added sugar is itself confusing. I get that one should only consume a certain amount of sugar in a day, but it makes no sense that the limit apply only to added sweeteners. Drinking 10 big glasses of orange juice a day is going to overload you with sugar, too.

I think what has happened here is that the FDA has allowed itself to be guided by what nutrition experts are talking about among themselves rather than what will actually help consumers make better decisions. After my experience with reading breakfast cereal labels, I'd be all for having the Nutrition Facts box tell people what percentage of a product's weight is accounted for by sugar. (You can do this yourself with information from the current label, but most people don't.)

It might even be a good idea to require that this percentage be disclosed in big type on the front of the package if the sugar content is above, say, 10 percent. Wouldn't it be fun if every box of Honey Nut Cheerios came with "THIS PRODUCT IS 32 PERCENT SUGAR" emblazoned on it? That's what I'd call a nutrition fact. This added-sugar stuff is more of a nutrition muddle.