Applied nutritional investigationStatistical review of US macronutrient consumption data, 1965–2011: Americans have been following dietary guidelines, coincident with the rise in obesity
Graphical abstract
Introduction
Since the late 1970s, the US government, following the American Heart Association (AHA) and much of academia, has consistently recommended lowering the dietary percentage of fat and saturated fat, as well as the absolute levels of dietary cholesterol, based on a theoretical link between those food components and higher risk for coronary heart disease [1]. This government guidance suggested that the reduction of dietary fat would be accompanied by a concurrent increase in the dietary share of carbohydrate. Taken together, these recommendations were also considered to be beneficial for the prevention of overweight and obesity, along with diabetes, cancer, and other chronic diseases [1].
Since the introduction of these dietary recommendations, rates of obesity and diabetes have increased dramatically [2]. The rapid increase in obesity rates has been explained in a number of ways [3], but is frequently attributed to the supposition that Americans have failed to adhere to dietary recommendations [4]. However, others suggest that dietary patterns of Americans have changed in response to advice to reduce their intake of fat, saturated fat, and cholesterol [5]. To our knowledge, no comprehensive analysis of consumption levels both before and after the endorsement of reduced-fat diets has been undertaken.
In this study, we use a set of government surveys between 1965 and 2011 to document patterns and changes in the consumption of the average adult since the earliest recommendations. We have three major findings. First, on average, adults in the United States have adhered to the government's dietary recommendations by shifting their proportional consumption of total calories from fats to carbohydrates. Fat consumption dropped from 44.7% in 1965 to 33.6% in 2011, whereas carbohydrate intake increased from 39% to 50.5% over the same period. Second, the reduction in the proportion of fat and cholesterol consumption arose largely from an increase in the daily intake of carbohydrate by about 260 calories from 1965 to 2011. Third, there is a high correlation (close to 90%) between the change in dietary pattern and the rise of obesity over the last 40 y. From 1971 to 2011, average weight and body mass index (BMI) have increased dramatically, with the percentage of overweight Americans increasing from 42.3% in 1971 to 66.1% in 2011.
The sources of data for this study are 10 US National Health and Nutrition Examination Surveys (NHANES) conducted by the National Center for Health Statistics (NCHS) of the Centers for Disease Control and Prevention (CDC) since the 1970s. We also analyzed their predecessor study, the 1965 US Department of Agriculture (USDA) Household Food Consumption Survey [6]. A 1997 study [7] using the 1976 to 1991 NHANES surveys showed that fat intake decreased and obesity increased during that 15-y period. However, contrary to our findings over a longer period, that study documented a concurrent drop in total caloric consumption. To our knowledge, except for the aforementioned article [7], this study presents the first comprehensive compilation of data from NHANES to examine the long-term trends in consumer dietary behaviors and concurrent obesity levels.
The second part of this study provides an overview of the US governmental dietary recommendations. We then describe the data source and research methods and present the results on consumer dietary patterns and correlation with significant increases in obesity.
Section snippets
History of macronutrient intake recommendations
In 1961, spurred by emerging medical and epidemiologic research, the AHA issued dietary recommendations to “reduce the intake of total fat, saturated fat, and cholesterol” [8]. In 1977, the US Senate Select Committee on Nutrition and Human Needs issued Dietary Goals for the United States, which recommended that fat consumption be reduced to 30% of energy intake, and that carbohydrate consumption be increased to account for 55% to 60% of energy intake [1].
Following this report, Dietary
NHANES data and research methods
To examine the long-term dietary consumption of the US population, we compiled detailed individual-level consumption from NHANES since the 1970s. Under the auspice of the NCHS, a division within the CDC (and ultimately, the DHHS), the NHANES has been conducted periodically since 1971 to assess the health and nutritional status of the US population by means of standardized interviews and physical examinations. The data collected include individual-level caloric consumption and body weight
Americans' caloric intake, 1965–2011
Trends in American caloric intake on average reflect the USDA/DHHS's recommendations regarding the consumption of fat and carbohydrate as a share of total calories. According to the 1965 USDA survey, fat consumption comprised 44.7% of adult Americans' diets, compared with 39% for carbohydrate. Even by 1971, those numbers had changed significantly, with fat down to 37.5% and carbohydrate up to 45.6%. By 1999, fat consumption reached a trough of 32.4%, whereas carbohydrate consumption hit its
Conclusion
In the first comprehensive statistical analysis using all available NHANES surveys, this study demonstrated that general adherence to government dietary recommendations to decrease fat share of total dietary intake has been accompanied by a rapid increase in obesity rates. The results from this study compel a full analysis of the potential causal relationship between Americans seeming adherence to the government's nutrition recommendations and obesity.
Acknowledgments
The authors acknowledge Anna Blatz for her statistical work on this article, and Nina Teicholz, for her support and editorial contributions.
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The authors have no conflicts of interest to report.