(Adds quotes from court, stats on sweetener market)

By Olga Grigoryants and Dan Levine

LOS ANGELES, Nov 4 (Reuters) - Corn refiners cannot "make stuff up" and claim that high fructose corn syrup is the same as sugar, an attorney for big sugar processors said in court on Wednesday.

Lawyers delivered opening statements in a trial pitting sugar processors against major corn refiners including Archer Daniels Midland Co and Cargill Inc. The billion-dollar lawsuit could shape how consumers view two bitter foes in a deteriorating U.S. sweetener market.

Several sugar refiners including global leader ASR Group sued in 2011, alleging that a corn trade group's ad campaign describing high fructose corn syrup as "corn sugar" and "natural" was false. The corn refiners countersued, saying the Sugar Association falsely claimed in its newsletter that corn syrup causes obesity and cancer.

The case comes amid a decline in sweetener demand. The U.S. slowdown is due in part to concerns about high rates of obesity and diabetes.

In a Los Angeles federal courtroom on Wednesday, sugar attorney W. Mark Lanier said sugar is sugar and corn syrup is not.

"You can look at Beyonce and (Arnold) Schwarzenegger," Lanier said. "They both are human and they both have bodies, but you can see the difference."

But Dan Webb, an attorney for the corn refiners, said both sugar and corn syrup have the same impact on the body, and the same amount of calories.

"One is crystal, one is liquid. They both are sugars," Webb said.

Webb said sugar processors were not damaged because of any statements made by corn refiners, having posted "record profits and record sales."

In 1999, the average American consumed 85.3 lb of corn sweeteners per year, compared with 66.4 lb of sugar, according to U.S. Department of Agriculture data. However, by 2014 corn sweetener consumption had dropped to 60.7 lb, while sugar consumption stood at 68.4 lb.

Overall, the average American consumed 131.1 lb of sweetener in 2014, down from 153.2 lb in 1999.

The U.S. Food and Drug Administration in 2012 ruled that corn syrup, used to sweeten foods including soda, could not be called sugar. The sugar growers are seeking $1.1 billion in compensatory damages over the prior advertising campaign, plus punitive damages and fees, Lanier said on Tuesday.

The corn refiners are seeking about $530 million in their countersuit.

Asked if a negative verdict would materially impact ADM, spokesman David Weintraub told Reuters on Tuesday that the company has "ample flexibility to handle any range of situations" with access to $6.4 billion of short-term liquidity.