WASHINGTON — Food labels that help U.S. shoppers decipher nutrition content are set to get their first makeover in 21 years.

The changes include updates to the nutrition facts panel on most foods sold in grocery stores and a revision to serving sizes, according to an online summary of two proposals the FDA sent to the White House for review. The full details of the draft regulations can’t be viewed yet by the public, and the FDA declined to comment on its plans.

The government is largely playing catch-up as the nation’s eating habits, food trends and advancements in obesity research have evolved since 1993, when food labels bearing basic calorie counts and fat grams became standard. The new labels will likely make calories more prominent, differentiate between natural and added sugars and make serving sizes more realistic.

“There wasn’t much supersizing 20 years ago,” Walter Willett, the nutrition department chairman at Harvard University’s School of Public Health in Boston, said in a telephone interview. “The world is changing about us and the nutrition facts panel hasn’t kept up.”

The Obama administration has pushed for uniform nutrition labels in an effort to reduce the U.S. obesity rate, which has more than doubled since 1980 to 78 million people in 2012, according to the Centers for Disease Control and Prevention.

The food industry began a voluntary front-of-package labeling system in 2011 in response to first lady Michelle Obama’s campaign against obesity and the FDA’s push for more accurate nutritional data.

Making calories more prominent and eliminating the line listing calories from fat may be useful for consumers, said Brian Kennedy, a spokesman for the Washington-based Grocery Manufacturers Association, whose members include Kraft Foods Group Inc. and General Mills Inc.

“The public health perspective that led to the nutrition facts panel in the early 1990s has shifted over the past 20 years, away from total fat and fatty acids and toward calories,” Kennedy said in an e-mail.

Draft regulatory proposals by the FDA are first sent for review to the White House’s Office of Management and Budget, a procedure that is supposed to be completed within 90 days.

Michael Jacobson, executive director at the consumer group Center for Science in the Public Interest, expects the FDA may make the proposals public by March 20.

He said that in addition to calories, the FDA may tinker with some daily values, including those for sodium, that tell consumers how much of the recommended amount of nutrition they’re consuming.

The recommended limit now is 2,400 milligrams per day while the CDC reduced sodium intake guidelines to 2,300 milligrams a day to as low as 1,500 milligrams per day for people 51 years and older and black people of any age and those with high blood pressure or diabetes, about half the population.