Bottles of Budweiser Select 55 are seen on a shelf at a grocery store Tuesday in Des Moines, Iowa.

Milwaukee ? How low can beer makers go? Having conquered the beer-belly set, some of the nation’s biggest brewers are trying to win over the six-pack-ab crowd with ultra-low-calorie suds.

The question is: Are drinkers willing to sacrifice flavor and a bit of the buzz? And: How long before beer gets turned back into water?

Most regular American beers, such as Budweiser, have about 150 calories and 5 percent alcohol, while most light beers contain around 100 calories and 4 percent alcohol.

The new brews, MillerCoors’ Miller Genuine Draft 64 and Anheuser-Busch InBev’s Select 55, are well below that. Their calorie counts are in their names, and they both contain less than 3 percent alcohol. Guzzling a whole MGD 64 or Select 55 is like taking a few swigs of a Bud.

Drinkers speak to an unavoidable tradeoff: To cut calories, beer companies reduce the amount of malted barley and other grains that are fermented during the brewing process. That, in turn, reduces the amount of alcohol in the brew. The result is a beer more like its main ingredient, water.

“You start producing something that could taste very, very thin,” says Thomas Shellhammer, professor of fermentation science at Oregon State University. “That would be the challenge for the brewer, to produce something that still tastes like beer.”

Light beers account for about half of the $99 billion-a-year beer market in the U.S., according to the Beverage Information Group, a market research firm. But the market for super-low-calorie is likely small, says Eric Schmidt, manager of information services.

MillerCoors says MGD 64 (slogan: “As light as it gets”) has sold twice as much in its first year as Miller Genuine Draft Light, which it replaced a year ago. It would not release specific figures.

After a few weeks of testing Select 55 in 15 markets, Anheuser-Busch decided to expand into a dozen more starting this month.

David Mitchell has been drinking MGD 64 since its release and says he prefers its taste to that of Coors Light, his previous beer of choice. “It’s almost like drinking a glass of water, but it has the beer taste,” says the 41-year-old from Gilbert, Ariz.