Clarification: An earlier version of this article said that the Pentagon has proposed cutting a $1.4 billion subsidy. The budget proposal would reduce the subsidy by more than two-thirds over three years; it would not eliminate it. This version has been updated.

Sharyn and John Thomas live at Fort Belvoir with their sons, Liam, left, and Patrick. They often shop at the base commissary, the busiest in the world. (Sarah L. Voisin/The Washington Post)

Over the years, Sharyn Thomas has found ways to stretch the household budget for her family of four. The Navy petty officer second class, 28, clips coupons and compares prices at several grocery stores — and the commissary at Fort Belvoir, in Fairfax County — to get the best deals on food.

Now her grocery bill may be going up.

The Defense Department has proposed reducing spending by cutting some retirement and other benefits for troops next year, including slashing by two-thirds a $1.4 billion subsidy to commissaries that allows goods to be sold at heavily discounted prices.

The Defense Commissary Agency estimates that a family of four saves about $4,509 annually shopping at a commissary rather than a local grocery store, because at the military version of a supermarket, goods are sold at cost plus 5 percent. A single service member saves about $1,553 a year.

“It would really stink to have some of those things that we do depend on to be cheaper” cost more, Thomas said. “But at the same time, we’re a military family. We’re adaptable. That’s our M.O.”

The proposed cuts would not affect the Basic Allowance for Subsistence (BAS), which is part of a soldier’s pay. Enlisted troops who do not live in barracks are paid an extra $357.55 a month to cover the cost of groceries, regardless of rank, marital status or number of children. Officers receive $246.24.

But the impact of the proposed cuts has many people worried.

“It is a not-insignificant cut that would affect the monthly finances of a lot of our families, especially our more junior enlisted families,” said AnnaMaria White, an active-duty Marine Corps spouse and public relations manager for Blue Star Families, an organization that supports military families.

White noted that the cuts also will affect military retirees, who are on a fixed income and, in many cases, still shop at commissaries. “If you raise their food prices, that is in effect a retirement cut,” she said.

There are 245 commissaries worldwide, 10 in the Washington area. The store at Fort Belvoir, where Thomas’s family shops, is the busiest in the world. It had $101.1 million in sales in 2013 and 1,112,359 transactions.

Fort Meade, in Anne Arundel County, also does a high-volume business. Its commissary had $73.5 million in sales last year and 1,010,763 transactions. The 10 area commissaries accounted for $446.1 million in sales last year, in 5,914,322 transactions.

Sen. Mark R. Warner (D-Va.) thinks slashing the commissaries’ budget is premature, and he has proposed legislation to block the cuts.

He has said he would rather delay a decision until after the Military Compensation and Retirement Modernization Commission, which is reviewing pay, benefits and retirement, issues its report in February 2015.

“Before that is finished, to single out commissaries for what is basically a 70 percent cut when you’re disproportionately hitting junior enlisted men and women, that could cost them $3,000 a year, I can’t go and say this makes sense when everybody else’s pay and retirement systems are not being touched,” Warner said.

But not everyone is alarmed. John Thomas, Sharyn’s husband and a disabled veteran who spent four years in the Air Force, said he considers commissaries a perk, one he’s willing to live without, even if it means paying more for groceries.

He would gladly sacrifice buying cheaper milk if it meant that his family’s health benefits weren’t touched. He and his wife have two boys, and their oldest son is autistic.

“I know that a lot of people are up in arms about it, and I should probably be breathing fire about, ‘How dare they cut our benefits,’ ” said Thomas, 30. “Health care and some of the other things are just so much more important.”