Grain-based foods maintained their position as the leading food group in the diet during the first decade of the 21st century, according to a report published recently by the Economic Research Service of the U.S. Department of Agriculture. While overall intake of grains fell slightly between 2000 and 2010, the decrease was consistent with an overall modest retreat in caloric intake during the period.

The data were published in the December issue of Amber Waves, an E.R.S. publication. “A Look at Calorie Sources in the American Diet,” was written by Sarah Rehkamp, an agricultural economist with the U.S.D.A.

Daily intake of grains in 2010 totaled 581 calories, down 2.5% from 596 calories in 2000. Grains’ share of total caloric intake held nearly unchanged, at 23.4%, versus 23.5% in 2000.

Overall caloric intake during the period slipped to 2,478 calories per day, down 3% from 2,540 calories in 2000.

The figures were based on the E.R.S. loss-adjusted food availability data, calculated based on the supply of food available for consumption and adjusted downward to approximate actual consumption by estimating and subtracting spoilage and other losses that occur from farm to retail and in grocery stores, restaurants and homes.

The aggregate figures around 2,500 calories are well beneath estimated American energy intake calculated using other methods, generally placed closer to 3,500 calories per day.

Plant-based food sources, including grains, fruits, vegetables, sugar and plant-based added fats accounted for 71% of caloric intake in 2010, up from 70% in 2000.

The second largest source of calories in the diet after grains was added fats (plant-based), at 518 per day, up 8% from 480 calories in 2000. Added vegetable fats gained share over the course of the decade, accounting for 21% of caloric intake in 2010, versus only 19% in 2000.

The 2 percentage point share gain for added fats was the largest of any single food group. The largest share loss occurred in sugars. At 369 calories, daily sugar intake fell 11% from 416 calories in 2000. The share of caloric intake accounted for by sugar slipped to 14.9% in 2010 from 16.4% in 2000.

Fruits and vegetables did not fare well over the course of the decade with fruits accounting for 81 calories per day in 2010, down 8% from 88 calories in 2000. Vegetables slid to 126 calories in 2010, down 11% from 141 calories in 2000.

Nuts performed impressively during the 2000s, with daily caloric intake jumping 26% to 72 in 2010, from 57 in 2000. Share of caloric intake for nuts rose to 2.9%, up seven tenths of a per cent from 2.2% in 2000.

Among animal sources of calories, the meat, poultry and fish category was largest and weakest. At 416 calories, daily intake of meat poultry and fish fell 5% from 438 in 2000. Share of caloric intake for the category fell to 16.8% in 2010 from 17.2% in 2000.

A period of extraordinary growth for certain dairy categories, notably yogurt, apparently did not translate into overall growth for the dairy sector. Daily consumption of dairy in 2010 was 234 calories, down 4.5% from 245 calories in 2000. The dairy “share of stomach” fell to 9.4% in 2010 from 9.6% in 2000.

Intake of added animal fats rose to 44 calories per day in 2010, up 7% from 41 calories in 2000. Share of caloric intake for added fats climbed to 1.8% in 2010, from 1.6% in 2000.

Daily consumption of eggs equaled 37 calories in 2010, down 2.6% from 38 calories in 2000. Share of stomach held steady over the decade at 1.5%.