WASHINGTON — Calorie management accounts for a large proportion of the guidance in the 2010 Dietary Guidelines for Americans, and grain-based foods are at the heart of the discussion.
The second chapter in the guidelines, “Balancing Calories to Manage Weight,” features extensive discussions around portion control as a way to deal with rising obesity rates.
“The current rates of overweight and obesity among virtually all subgroups of the population in the United States demonstrate that many Americans are in calorie imbalance — that is, they consume more calories than they expend,” the D.G.A. said. “To curb the obesity epidemic and improve their health, Americans need to make significant efforts to decrease the total number of calories they consume from foods and beverages and increased calorie expenditure through physical activity.”
The report cited data indicating a doubling and in some cases trebling of U.S. obesity rates since the 1970s.
At the center of the chapter is a table listing principal sources of calories among Americans. Five of the top six sources on the list, which was derived from the 2005-06 National Health and Nutrition Examination Survey (NHANES), were grain-based: grain-based desserts, yeast breads, pizza, pasta and tortillas.
“Although some of the top calorie sources by category are important sources of essential nutrients, others provide calories with few essential nutrients,” the report said. “Many of the foods and beverages most often consumed within these top categories are in forms high in solid fats and/or added sugars, thereby contributing excess calories to the diet. For example, many grain-based desserts are high in added sugars and solid fats, while many chicken dishes are both breaded and fried, which adds a substantial number of calories to the chicken.”
The chapter features extensive discussion of the background against which the obesity rate increases have occurred.
“The food supply has changed dramatically over the past 40 years,” the report said. “Foods available for consumption increased in all major food categories from 1970 to 2008. Average daily calories available per person in the marketplace increased approximately 600 calories, with the greatest increases in the availability of added fats and oils, grains, milk and milk products, and caloric sweeteners.
“Many portion sizes offered for sale also have increased. Research has shown that when larger portion sizes are served, people tend to consume more calories. In addition, strong evidence shows that portion size is associated with body weight, such that being served and consuming smaller portions is associated with weight loss.
“Studies examining the relationship between the food environment and B.M.I. have found that communities with a larger number of fast food or quick-service restaurants tend to have higher B.M.I.s. Since the 1970s, the number of fast food restaurants has more than doubled.”
Macronutrient proportions were left unchanged in the guidance from the 2005 report with 45% to 65% of energy from carbohydrates, 10% to 35% from protein and 20% to 35% from fat, for adults.
Advice on body weight management offered the scientific underpinnings of recommendations to increase intake of whole grains, vegetables and fruits.
“Moderate evidence shows that adults who eat more whole grains, particularly those higher in dietary fiber, have a lower body weight compared to adults who eat fewer whole grains,” the report said. “Moderate evidence in adults and limited evidence in children and adolescents suggests that increased intake of vegetables and/or fruits may protect against weight gain.”
Other specific advice for weight management all related to beverages:
o Reduce consumption of sugar-sweetened beverages
o Monitor intake of fruit juice for children
o Monitor calorie intake from alcoholic beverages.
In discussing sources of carbohydrates, the report appears to put a great premium on the nutrition in whole grains without citing any benefits from or even mentioning enriched grains. The report takes a dim view of the glycemic index as a guide for weight control.
“When choosing carbohydrates, Americans should emphasize naturally occurring carbohydrates, such as those found in whole grains, beans and peas, vegetables, and fruits, especially those high in dietary fiber, while limiting refined grains and intake of foods with added sugars,” the report said. “Glycemic index and glycemic load have been developed as measures of the effects of carbohydrate-containing foods and beverages on blood sugar levels. Strong evidence shows that glycemic index and/or glycemic load are not associated with body weight; thus, it is not necessary to consider these measures when selecting carbohydrate foods and beverages for weight management.”
Other guidance in the calorie management chapter includes reducing portion size both when eating at home and outside, eating a nutrient dense breakfast and limiting screen time.
The chapter also offers guidelines for physical activity, including an hour daily for children and 2.5 hours weekly for adults.