BOSTON — New federal rules requiring large restaurant chains to post nutritional information may not be enough to lower the national obesity rate, according to researchers at Tufts University in a study supported by the U.S. Department of Agriculture.

While restaurant chains with 20 or more locations will be required to provide the calorie content of their menu items, smaller chains and independent restaurants, which are exempt from such labeling and yet account for approximately half of the nation’s restaurants, were found to serve meals that exceed daily intake requirements by two or three times.

Researchers at the Jean Mayer U.S.D.A. Human Nutrition Research Center on Aging at Tufts University in Boston analyzed 157 meals, including side dishes, from 33 randomly selected independent or small-chain restaurants in the Boston area between June and August 2011. Samples included popular dishes from Mexican, American, Chinese, Italian, Japanese, Thai, Greek and Vietnamese restaurants.

Of the meals analyzed, 73% contained more than half of the Food and Drug Administration’s daily intake recommendation of 2,000 calories, and 12 meals exceeded the recommended daily amount. On average, the meals studied contained 1,327 calories.

Samples from the Italian, American and Chinese restaurants on average contained the most calories, while Vietnamese and Japanese meals averaged the lowest number of calories, at 922 and 1,027, respectively, which still exceed recommendations for a single meal.

“National recommendations for the prevention and treatment of obesity stress individual self-monitoring of food consumption, but there is little available information on the energy content of foods offered by restaurants that are not required to post nutrition information,” said Lorien Urban, Ph.D., an author of the study and postdoctoral scholar in the Energy Metabolism Laboratory at the center. “Given that an imbalance between energy intake and energy expenditure of only 100 calories per day can lead to a weight gain of between 6 and 15 lbs per year, our findings suggest that routine reporting of meal calorie content by all restaurants, not just large chains, would encourage individuals to make informed choices about their diet and would discourage restaurants from offering unhealthy portions.”