This paper investigates trends in disability in the U.S. population, particularly among people under age fifty. Even as the elderly have become less disabled, reported disability has risen for younger Americans, especially those ages 30-49. We suggest some possible explanations for rising disability levels, such as obesity, technological advances in medicine, and changing disability insurance laws. Obesity and its attendant disorders seem particularly associated with these trends, although the data are not definitive. Whatever its sources, rising disability among the young could have adverse consequences for public programs such as disability insurance, Medicare, and Medicaid.

Context Low-carbohydrate diets have been popularized without detailed evidence of their efficacy or safety. The literature has no clear consensus as to what amount of carbohydrates per day constitutes a low-carbohydrate diet.

Objective To evaluate changes in weight, serum lipids, fasting serum glucose, and fasting serum insulin levels, and blood pressure among adults using low-carbohydrate diets in the outpatient setting.

Data Sources We performed MEDLINE and bibliographic searches for English-language studies published between January 1, 1966, and February 15, 2003, with key words such as low carbohydrate, ketogenic, and diet.

Study Selection We included articles describing adult, outpatient recipients of low-carbohydrate diets of 4 days or more in duration and 500 kcal/d or more, and which reported both carbohydrate content and total calories consumed. Literature searches identified 2609 potentially relevant articles of low-carbohydrate diets. We included 107 articles describing 94 dietary interventions reporting data for 3268 participants; 663 participants received diets of 60 g/d or less of carbohydrates—of whom only 71 received 20 g/d or less of carbohydrates. Study variables (eg, number of participants, design of dietary evaluation), participant variables (eg, age, sex, baseline weight, fasting serum glucose level), diet variables (eg, carbohydrate content, caloric content, duration) were abstracted from each study.

Data Extraction Two authors independently reviewed articles meeting inclusion criteria and abstracted data onto pretested abstraction forms.

Data Synthesis The included studies were highly heterogeneous with respect to design, carbohydrate content (range, 0-901 g/d), total caloric content (range, 525-4629 kcal/d), diet duration (range, 4-365 days), and participant characteristics (eg, baseline weight range, 57-217 kg). No study evaluated diets of 60 g/d or less of carbohydrates in participants with a mean age older than 53.1 years. Only 5 studies (nonrandomized and no comparison groups) evaluated these diets for more than 90 days. Among obese patients, weight loss was associated with longer diet duration (P = .002), restriction of calorie intake (P = .03), but not with reduced carbohydrate content (P = .90). Low-carbohydrate diets had no significant adverse effect on serum lipid, fasting serum glucose, and fasting serum insulin levels, or blood pressure.

Conclusions There is insufficient evidence to make recommendations for or against the use of low-carbohydrate diets, particularly among participants older than age 50 years, for use longer than 90 days, or for diets of 20 g/d or less of carbohydrates. Among the published studies, participant weight loss while using low-carbohydrate diets was principally associated with decreased caloric intake and increased diet duration but not with reduced carbohydrate content.

The case for reduction of air pollution has been predicated primarily on the frequently observed relationship between pollution and mortality and morbidity. Because pollution control usually involves costs, a rational public policy will weigh the benefits against the costs. This study investigates another potential benefit from pollution reduction: namely, decreased use of medical care. We find a strong relationship between particulate matter and inpatient and outpatient care at ages 65-84 across 183 metropolitan statistical areas (MSAs). The relationship is statistically significant at a very high level of confidence even after the region and population size of the areas, education, real income, racial composition, use of cigarettes, and obesity are controlled for.

Objective:To examine whether televised food commercials influence preschool children's food preferences.

Design: In this randomized, controlled trial, preschool children viewed a videotape of a popular children's cartoon either with or without embedded commercials. Children were then asked to identify their preferences from pairs of similar products, one of which was advertised in the videotape with embedded commercials. Preschoolers' parents were interviewed to determine children's demographic characteristics and media use patterns.

Subjects: Forty-six 2- to 6-year-olds from a Head Start program in northern California.

Statistical Analyses: For demographic and media use characteristics, univariate data were examined and Student t and chi 2 tests were used to test for differences between the control and treatment groups. We calculated the Cochran Q statistic to assess whether the proportion of those choosing advertised food items was significantly higher in the treatment group than in the control group.

Results: Children exposed to the videotape with embedded commercials were significantly more likely to choose the advertised items than children who saw the same videotape without commercials (Qdiff = 8.13, df = 1, P .01).

Conclusions/Applications: Even brief exposures to televised food commercials can influence preschool children's food preferences. Nutritionists and health educators should advise parents to limit their preschooler's exposure to television advertisements. Furthermore, advocates should raise the public policy issue of advertising and young children, especially given the recent epidemic of childhood obesity and the ever-changing media environment.

Objective: Identifying parental behaviors that influence childhood obesity is critical for the development of effective prevention and treatment programs. Findings from a prior laboratory study suggest that parents who impose control over their children's eating may interfere with their children's ability to regulate intake, potentially resulting in overweight. These findings have been widely endorsed; however, the direct relationship between parental control of children's intake and their children's degree of overweight has not been shown in a generalized sample.

Research Methods and Procedures: This study surveyed 792 third-grade children with diverse ethnic and socioeconomic backgrounds from 13 public elementary schools. Parental control over children's intake was assessed through telephone interviews using a state-of-the-art instrument, and children were measured for height, weight, and triceps skinfold thickness.

Results: Counter to the hypothesis, parental control over children's intake was inversely associated with overweight in girls, as measured by body mass index, r = -0.12, p 0.05, and triceps skinfolds, r = -0.11, p 0.05. This weak relationship became only marginally significant when controlling for parents' perceptions of their own weight, level of household education, and children's age. No relationship between parental control of children's intake and their children's degree of overweight was found in boys.

Discussion: Previous observations of the influence of parental control over children's intake in middle-class white families did not generalize to 8- to 9-year-olds in families with diverse socioeconomic and ethnic backgrounds. The present findings reveal a more complex relationship between parental behaviors and children's weight status.

Children spend a substantial portion of their lives watching television. Investigators have hypothesized that television viewing causes obesity by one or more of three mechanisms: (1) displacement of physical activity, (2) increased calorie consumption while watching or caused by the effects of advertising, and (3) reduced resting metabolism. The relationship between television viewing and obesity has been examined in a relatively large number of cross-sectional epidemiologic studies but few longitudinal studies. Many of these studies have found relatively weak, positive associations, but others have found no associations or mixed results; however, the weak and variable associations found in these studies may be the result of limitations in measurement. Several experimental studies of reducing television viewing recently have been completed. Most of these studies have not tested directly the effects of reducing television viewing behaviors alone, but their results support the suggestion that reducing television viewing may help to reduce the risk for obesity or help promote weight loss in obese children. Finally, one school-based, experimental study was designed specifically to test directly the causal relationship between television viewing behaviors and body fatness. The results of this randomized, controlled trial provide evidence that television viewing is a cause of increased body fatness and that reducing television viewing is a promising strategy for preventing childhood obesity.

Selected by the editors of Contemporary Pediatrics as the most significant pediatric study of 1999. Also first printed in 1999, v 282, p1561-1567 JAMA