Fat. Salt. Carbs. At some point, all have been fingered as a culprit in America's poor diet.

But sugar is shaping up to be the next public enemy No. 1.

It's been the bad guy before, but a fresh batch of initiatives and studies are recasting sugar from its former status as a substance that might decay teeth and add a pound or two to one that contributes to life-threatening diseases. In some cases, it's even been cited as a toxin poisoning the entire country.

The most widely known recent measure surrounding sugar is the approved New York beverage ban, which bars the sale of large sodas and other sugary drinks. But larger initiatives are lurking in the background that could also affect sugar consumption. For one, new federal dietary guidelines will come out in 2015, and industry watchers expect revised consumption estimates for sugar.

And if anti-sugar proponents have their way, it could also end up on the radar of the Food and Drug Administration. On the FDA's list later this year will likely be proposed revisions to the 1990 Nutritional Labeling and Education Act. Potential revisions to nutritional labels, serving sizes and daily values could affect not only packaging but spur reformulation of the food inside and the need to address those changes in the marketing.

While the FDA has recommended daily allowances for sodium and fat, it has no such measure for sugar. The Center for Science in the Public Interest last month filed a petition asking the agency to address the issue by establishing a recommended safe level of added sugars, particularly in beverages. The American Heart Association advises that women consume no more than six teaspoons of added sugars per day and men no more than nine. CSPI said the average 20-ounce bottle of soda contains nearly 16 teaspoons of added sugars. It's unclear whether the FDA will address the petition.

Add to all this the media noise over New York Times reporter Michael Moss' recently released book, "Salt Sugar Fat: How the Food Giants Hooked Us," which argues that large packaged-food companies incorporated salt, fat and sugar into their products knowingly because they have addictive properties. In a 9,000-word excerpt in The New York Times Magazine, Mr. Moss featured former food-company executives and food scientists wringing their hands over their contributions to the obesity epidemic. In fact, the cover featured a quote from Robert I-San Lin, a former chief scientist for Frito-Lay: "I feel so sorry for the public."

The article includes a former Kraft exec making a connection between food-industry practices and those used by the tobacco companies -- an analogy that no one in the food industry wants to hear.

Mr. Moss did not respond to requests for an interview for this story.

Soda and snacks might be the biggest sugar sinners, but the fact is that in some form or other -- whether it be cane or high-fructose corn syrup -- sugar is in almost every processed food Americans consume. And if the sugar crusade broadens to the wider consumer population or the FDA requires label changes, companies may have no choice but to reformulate -- and tinkering with recipes could lead to serious sales consequences if taste profiles change significantly.

"These companies are certainly looking at the big picture," said Lee Sanders, senior VP-government and public affairs at the American Bakers Association, whose members include marketers such as Pepperidge Farm. "Consumers like the products that are on the shelves, so that's a hurdle [if requirements change], and you want to make sure you're being responsive to the consumers. ... Potentially, you could have a lot of new messages and concepts aimed at consumers."

The packaged-food industry in 2011 addressed some labeling concerns with a self-regulatory front-of-package label initiative. Ms. Sanders said that some companies are holding off on the front-of-label packaging until the FDA settles on revisions to the NLEA label rules because repackaging is a costly endeavor.

Despite watchdog groups and armchair nutritionists posting their theories on Facebook, the truth is there's relatively little research and data drawing direct lines from sugar to obesity and diabetes -- and when connections are made, the relationship is complex. But industry watchers expect more studies exploring those connections to be released in the next few years.

Michael Jacobson, exec director at CSPI, said that despite the fact that studies can be "fraught with limitations" and can never prove cause and effect, "the food industry should realize there's a huge amount of evidence that consuming too much sugar, particularly from beverages, poses a real health problem, and they should be putting more money toward encouraging people to consume low-sugar products."