Calories Count: Title and subTitle BreakBut Can Consumers Count on Them?

Excess energy intake contributes to weight gain. Although energy output can help balance energy intake for weight control over time, weight loss for most sedentary people can be achieved only by reducing energy intake.^{1 - 2} Despite long-held assumptions that diet composition might influence the rate and overall capacity for weight loss, randomized controlled trials have recently documented that regardless of shifts in total protein, carbohydrate, or fat intake, the bottom line in achieving successful weight loss is adherence to a diet that is reduced in total energy intake.^{3 - 4}

Behaviorally, this involves reducing the total number of calories consumed to achieve an energy deficit over time. Energy-dense foods and beverages such as those with added sugar or fat have more energy per unit weight of food compared with non–energy-dense foods such as fruits and vegetables that contain more water or fiber.⁵ Both energy density and increased portion size appear to influence excessive energy intake and increased risk for overweight.⁶ The standard unit of measure is kilocalories or kilojoules per 100 g of the food or beverage consumed, but US residents typically refer to the number of calories per serving as the reference point for its total energy content, which is presented on a label or menu.

When the total number of calories needed each day to control weight is known and understood, an individual can track caloric intake in an attempt to undercut that number and thereby achieve a caloric deficit or negative energy balance.⁷ Generally, a deficit of 500 calories per day can achieve a 1-lb weight loss per week because a net reduction of 3500 calories is required to lose 1 lb of body weight.⁸ Although known variability exists due to genetics, sex, body weight, and other factors, estimating total caloric intake per day by self-monitoring the caloric content of foods consumed represents a potentially effective strategy for weight loss.^{1 - 2} Because weight loss maintenance requires even less energy,⁹ knowing the caloric content of foods and relying on the accuracy of labeled amounts become paramount in attempting long-term weight control.

In this issue of JAMA, the study by Urban and colleagues¹⁰ assessed the accuracy of stated energy contents of restaurant foods. Bomb calorimetry was used in this study and it is considered a highly accurate method for measuring gross energy content according to the heat produced at combustion and assessed by increased water temperature.^{11 - 12} These values are converted to caloric content by applying appropriate US Food and Drug Administration multiplicative factors (Atwater factors) associated with the macronutrient content of each food (eg, fat = 9.4 kcal/g, protein = 5.65 kcal/g, and carbohydrate = 4.15 kcal/g).

Urban et al¹⁰ randomly selected low- and high-energy content foods from 7 quick-serve and 7 sit-down chain-type restaurants across 3 states. Foods were ordered, stored, and transported to the respective laboratories where they were processed, frozen, and shipped to the Massachusetts site for energy analysis. This study used carefully standardized methods and performed duplicate measures on a subset of the samples collected.

Discrepancies in caloric content were noted between some of the measured samples and the stated amounts. Of the 269 foods collected from 42 restaurants, 108 (40%) were found to have measured energy at least 10 kcal/portion higher than the stated amounts, 141 (52%) were found to have at least 10 kcal/portion lower than the stated amounts, and 50 (19%) contained at least 100 kcal/portion higher than the stated amounts. Discrepancies were greater and more frequent in sit-down restaurants that featured foods with lower stated energy contents (<600 kcal/portion) compared with foods with higher stated energy contents (≥600 kcal/portion), which actually had lower energy contents than stated. This study remeasured the 10% of foods with the highest positive discrepancies and had similar findings the second time; portion size appeared to account for part of the inaccuracy of the stated energy amounts. Desserts, carbohydrate-rich foods, and salads contained significantly more energy contents than the stated amounts.

While it is reasonable to wonder why desserts, snack foods, and candy bars would be consumed by weight-conscious people, findings from the National Health and Nutrition Examination Survey Data 2005-2006 illustrate that the top-ranked source of energy intake in the United States is grain-based desserts, with several other snack foods ranking high on the list.¹ Collectively, snacks, desserts, and pizza represent approximately 30% of the population's average caloric intake.¹

Among adolescents aged 14 to 18 years, who represent the age group with the highest energy intake, that figure is approximately 40% of total calories consumed. Likewise, from 1977 to 1995, the number of meals and snacks consumed in non–fast-food and fast-food restaurants increased by 150% and 200%, respectively.¹ From 1970 through 2008, expenditures for food at home decreased by 42% while expenditures for food away from home increased by 26%.¹ Thus, some fundamental issues raised in the study by Urban et al¹⁰ deserve further consideration.

With the passage of the US Patient Protection and Affordable Care Act,¹³ labeling of caloric content is mandated in restaurants and by food vendors with more than 20 locations. Accuracy and standardization of menus, serving sizes, ingredients, and preparation techniques are essential to constituting truth in labeling along with regular monitoring to ensure these standards are being maintained.

Perhaps most important, the value of this labeling law can be enhanced considerably through effective public health education campaigns to facilitate its use. Primary prevention efforts could be markedly improved through better parental awareness of the caloric needs of their children and, ideally, the capacity to role model their own energy balance. Limited data document that adult consumers are often unable to estimate caloric differences across unlabeled food items; however, among those who read posted caloric contents, reduced caloric intake occurs.¹⁴ Prevention and treatment of overweight and obesity require change in the environment as well as in personal behavior. However, it is notable that only a few studies, mostly in older adults, specify whether monitoring daily caloric intake based on labeled amounts facilitates weight control.

Just as balancing a budget can prevent debt, balancing caloric intake with output can prevent added pounds. However, US residents seem to be struggling with both balancing acts. New, innovative, and effective approaches to teaching about energy balance and calorie control are greatly needed.