WASHINGTON — Driven in part by the impact of the economic recession, daily caloric intake among working age adults declined by 118 calories, or roughly 5%, between 2005-06 and 2009-10, according to a study issued by the Economic Research Service of the U.S. Department of Agriculture. Adjusted for demographic shifts that occurred during this period, the E.R.S. estimated the reduction in caloric intake at 78 calories per day, or 3.4%. On an adjusted basis, calories consumed of food away from the home (F.A.F.H.) fell by 15% while the number of meals fell by 11%. The researchers described the figures as “relatively large” given what had been consistent growth in the share of F.A.F.H. for decades. The study indicated that most of the improvement in diet quality was not because of the decline in F.A.F.H consumption. “The improvements in diet quality are consistent with previous research that suggests that recessions can have a positive effect, on average, for some individual health outcomes,” the researchers said. They added that increased consumer focus on nutrition also may have been an important factor in the improved eating.