Since the publication of Dr. Atkins' Diet Revolution in 1972 (1), low-carbohydrate diets (LCDs) and high-protein diets have gained prominence in the United States. In recent years, LCDs have regained popularity, as evidenced by the publication of such books as Dr. Atkins' New Diet Revolution (2), The New Sugar Busters! (3), and The South Beach Diet (4).

In 2005, dietary experts from government, academia, and industry convened the International Life Sciences Institute North America Technical Committee on Carbohydrates to review scientific evidence about the healthfulness of LCDs. This committee identified gaps in existing research, including a need to assess awareness and trends in adoption of LCDs (5). Although efficacy (6) and use of LCDs have been explored (7), public awareness and perceived healthfulness of LCDs have not been examined in a nationally representative sample. Therefore, we examined public awareness, use, and perceptions of LCDs.

The purpose of our research was to use national data to explore the correlates of awareness, use, and perceptions of LCDs, including sociodemographic characteristics and key communication variables. The efficacy, effectiveness, and safety of LCDs have been a matter of scientific debate. Given the controversy surrounding these issues, we neither endorse nor denounce LCDs but rather describe national patterns. To our knowledge, the 2005 Health Information National Trends Survey (HINTS) provides the first available nationally representative data that document awareness, use, and perceptions of LCDs, and we help fill a gap in the literature by analyzing these data to reveal trends.

Weighted percentages for sociodemographic characteristics of the sample are summarized in Table 1. Overall, awareness of LCDs was high; 86.6% of total respondents reported that they were aware of LCDs. Awareness was associated at the bivariate level with being a woman, being a college graduate, being non-Hispanic white, having an annual income of $50,000 or more, being 50 to 64 years of age, having an approximate mean body mass index (BMI) of 27 kg/m², and reporting no behavioral change in response to new nutrition recommendations. Approximately 17% of respondents reported that they had tried an LCD during the past 12 months. Use of LCDs was significantly associated at the bivariate level with being a woman; being a college graduate; reporting a race or ethnicity other than non-Hispanic white, non-Hispanic black, or Hispanic; having an annual income of $50,000 or more; being aged 50 to 64 years; having an approximate mean BMI of 29 kg/m²; having been exposed to "a lot" or "some" nutrition information on the Internet during the past 12 months; and having been exposed to "a lot" or "some" nutrition information from a health care professional during the past 12 months. One-third (33.7%) of respondents perceived LCDs to be a healthy way to lose weight. Among respondents who reported that they had tried an LCD during the past 12 months, 58.1% reported that they thought it was a healthy way to lose weight (data not shown). Reported agreement with the healthfulness of LCDs was significantly associated at the bivariate level with being a man, having less than a high school education, being Hispanic, having an annual income <$25,000, reporting changing behavior in response to new nutrition recommendations, having been exposed to "a lot" or "some" nutrition information from a health care professional during the past 12 months, being ≥75 years of age, and having an approximate mean BMI of 27 kg/m².

Table 2 displays the results of the multivariate analyses to examine independent correlates of awareness, use, and perceptions of LCDs. In model A, awareness of LCDs was higher among respondents with a high school education or more and among respondents with a high BMI. Awareness of LCDs was lower among non-Hispanic blacks and Hispanics than among non-Hispanic whites. In model B, use of LCDs was higher among women than among men and higher among respondents with a high BMI than among respondents with a low BMI. In model C, respondents with a high school or college degree were less likely to agree that LCDs are a healthy way to lose weight than were respondents with less than a high school education. Respondents who reported that they change their behavior in response to new nutrition recommendations were more likely to agree that LCDs are a healthy way to lose weight than were respondents who reported that they do not change their behavior.

Because of the lack of consensus among health professionals about LCDs, using these diets to manage weight is controversial. Insight into the correlates of awareness, use, and perceptions of LCDs helps show how sociodemographic characteristics and communication behaviors relate to the way people react to an environment of multiple and occasionally contradictory nutrition messages. Our results showed high awareness of LCDs among Americans, which is not surprising because data for HINTS 2005 were collected when LCDs were highly publicized in the media.

Respondents who were highly educated, were non-Hispanic white, and had a high BMI were most likely to be aware of LCDs. Among respondents who were aware of LCDs, those with a low level of education and who reported a high likelihood of changing their behavior in response to new nutrition recommendations were more likely to perceive LCDs as a healthy way to lose weight. This pattern of awareness is consistent with the "knowledge gap" theory that health knowledge is unequally distributed. This gap is characterized by a discrepancy between people from high socioeconomic status (SES) groups who tend to have more information (or are "information rich") than do people from low SES groups (who are "information poor") (9). Correlates of use and perceived healthfulness of LCDs were different from those of awareness, which suggests that factors that may influence use of LCDs do not necessarily drive perceptions of their healthfulness. More than half of respondents who had tried LCDs reported that they perceived them to be a healthy way to lose weight. Results also suggested that respondents who regard LCDs as a healthy way to lose weight may be more likely to pursue dietary recommendations before scientific evidence of efficacy and safety are available.

Estimates of LCD use in our sample were approximately 5 times greater than those found in a previous study, which reported a prevalence of 3.4% (7). However, the data used in that study were collected in 2002, and data used for our study were collected in 2005, which suggests that awareness and use of LCDs has increased over time.