Worried about trans fat or salt? That's a little old-school. If you want to stay current on dietary villains, you'll want to start thinking about sugar.

When looking at the failings of the American diet, the new culprit is sugar. Some think that the no-sugar call is simplistic, though, and that there's no single villain.

Breaking down its many names

Fructose

Found naturally in fruit, fructose is about 70% sweeter than glucose, the simple sugar that's the body's main source of energy. Fructose has a low glycemic index, meaning it barely budges a person's blood sugar. But beware: Fructose in juice and processed foods goes straight to the liver, and it's thought to be a major contributor to metabolic syndrome, a collection of problems that can put a person on the path toward diabetes, heart disease or stroke.

Sucrose

This is the fancy name for table sugar, the sweet stuff distilled from sugar cane or sugar beets. It's actually a 50-50 combo of two simpler sugars, fructose and glucose. Like all sugars, it has about 16 calories per teaspoon. It raises blood sugar faster than straight fructose mainly because it's easier to digest.

High-fructose corn syrup

The name misleads. HFCS has about 55% fructose and 45% glucose, making it practically identical to table sugar (sucrose). No better and no worse. The trouble, says UC San Francisco's Dr. Robert Lustig, is that HFCS is cheap and easy to make — which is why it shows up in so many foods.

Honey

Like HFCS, honey has slightly more fructose than glucose, although the exact balance depends on the flower source. Some research suggests that honey creates a different hormonal response than table sugar or HFCS and may not be as fattening.

Agave syrup

Often touted as a safe, natural alternative to table sugar, the syrup from the agave plant is up to 90% fructose — far more than even so-called high-fructose corn syrup.

Where sugar hides out

Sugar foe Dr. Robert Lustig says he doesn't worry about sugars naturally found in whole fruits and vegetables because they come with a healthy dose of fiber. In his view, it's pretty much impossible to OD on sweet stuff if you eat just natural, unprocessed foods.

It's the added sugars that should be avoided, Lustig says, not because they're chemically different but because all of that unnatural sugar-without-the-fiber can throw your system off balance.

But food labels don't list added sugars. So how much is hiding in your food? Here are some estimates:

Ketchup

Serving: 1 tablespoon

2/3 teaspoon sugar

Corn flakes

Serving: 1 cup

1/3 teaspoon sugar

Peanut butter

Serving: 2 tablespoons

1/4 teaspoon sugar

Bagel

Serving: 1 plain bagel

1 1/4 teaspoons sugar

Sweetened applesauce

Serving: 1 cup

4 teaspoons sugar

Fruit-flavored yogurt

Serving: 6 ounces

About 5 teaspoons sugar

Peaches in heavy syrup

Serving: 1 cup

9 teaspoons sugar

Cola

Serving: 12-ounce can

10 teaspoons sugar

Teriyaki sauce

Serving: 1 tablespoon

1 1/2 teaspoons sugar

Graham crackers

Serving: 2 graham crackers

2 teaspoons sugar

Source: USDA Database for Added Sugar Content of Selected Foods 2006; Kikkoman Corp., Nabisco, Welch's, Torani