Clinical implications of trends in food intake among US adolescents.

Abstract

The accompanying research article by Cavadini and colleagues raises many concerns over the eating patterns of US adolescents and the possible long-term health implications of these behaviors. Analyzing data collected from 1965 through 1996 as part of the Continuing Survey of Food Intakes by Individuals (CSFII), the authors found some disturbing trends in eating patterns and weight status of teens, including a substantial increase in body mass index (BMI). Other national surveys, including the National Health and Nutrition Examination Survey (NHANES), have also shown a temporal increase in body mass index (BMI).1 According to new guidelines on the detection and treatment of overweight among youth, a BMI value that is equal to or greater than the 85th percentile, but less than the 95th percentile, classifies a teenager as at-risk for overweight, while a BMI value equal to or greater than the 95th percentile classifies a teen as overweight.2 Using these guidelines, the prevalence of overweight among US adolescents has more than doubled since 1965.3 The exact reasons for this dramatic increase in overweight among US youth are not known. Genetic factors alone cannot account for such a striking increase in obesity in such a relatively short time span. Environmental factors have been suggested, such as an increase in energy and/or fat consumption, but the data reported by Cavadini and colleagues only partially support this hypothesis. The intake of both energy and total fat among US adolescents appears to have declined from 1965 to 1989, after which time they began to increase. These relative changes in calorie and fat consumption are not, however, consistent with the increases in BMI. Clearly, other factors must be involved—such as a decrease in energy expenditure secondary to a decrease in physical activity and a change in the overall composition of the dietary intake. Cavadini and colleagues reported a dramatic increase in the consumption of carbonated beverages accompanied by a reduction in the consumption of fluid milk. Harnack and colleagues, also using CSFII data, reported that carbonated beverages replace milk in the diets of adolescents, thus increasing the intake of sugar and other caloric sweeteners and reducing the nutrient density of the diet.4 In fact, national data suggest that sweeteners and added sugars alone provide more than 16% of the total calories and 12% of total carbohydrate consumed by US adolescents.5 This is particularly alarming in light of recent increases in BMI values and the prevalence of overweight among adolescents.1,3 Another concern raised by the increase in carbonated beverage consumption accompanied by the decrease in fluid milk consumption is the resulting reduction of intakes of calcium and vitamin D. Calcium intake among adolescents is suboptimal. Stang and colleagues, also using data from the CSFII, showed that as many as two-thirds of US adolescents do not consume at least 75% of the Daily Recommended Intake or Recommended Daily Allowances for calcium.6 This trend is more pronounced among female teens. The long-term implications of reduced intakes of calcium and vitamin D may include a reduction in peak bone mass and a concomitant increased risk of osteoporosis. Recent data suggest that the consumption of carbonated beverages increases an adolescent's lifetime risk of bone fractures, particularly among physically active females.7 A disconcerting clinical situation is imaginable among young and middle-aged adults: their chronic long-term consumption of carbonated beverages leads to a greatly reduced peak bone mass, compounded by obesity which causes them to carry excessive weight and prevents them from participating in moderate to strenuous physical activity. Certainly, the optimal time for intervention related to improving dietary intake and maintaining a healthy body weight is during childhood and adolescence. The Guidelines for Adolescent Preventive Services suggest that annual screening and education be provided to adolescents around the issues of eating a healthy diet and maintaining a healthy weight.8 The study by Cavadini and colleagues clearly illustrates the need for providing routine anticipatory guidance to children, adolescents, and their families with regard to eating and physical activity behaviors. Bright Futures in Practice: Nutrition,9 and the soon-to-be-released Bright Futures in Practice: Physical Activity, provide guidelines for developmentally appropriate anticipatory guidance on these topics that can be implemented in clinical settings.