Abstract
Competing theories attempt to explain changes in total energy (TE) intake; however, a rigorous, comprehensive examination of these explanations has not been undertaken. Our objective was to examine the relative contribution of energy density (ED), portion size (PS), and the number of eating/drinking occasions (EOs) to changes in daily TE. Using cross-sectional nationally representative data from the Nationwide Food Consumption Survey (1977-78), Continuing Survey of Food Intakes of Individuals (1989-91), and National Health and Nutrition Examination Surveys (1994-98 and 2003-06) for adults (aged ≥19 y), we mathematically decompose TE (kcal/d) to understand the relative contributions of each component-PS (grams/EO), ED (kcal/g/EO) and EO(number)-to changes in TE over time. There was an increase in TE intake (+570 kcal/d) and the number of daily EOs (+1.1) between 1977-78 and 2003-06. The average PS increased between 1977-78 and 1994-98, then dropped slightly between 1994-98 and 2003-06, while the average ED remained steady between 1977-78 and 1989-91, then declined slightly between 1989-91 and 1994-98. Estimates from the decomposition statistical models suggest that between 1977-78 and 1989-91, annualized changes in PS contributed nearly 15 kcal/d/y to increases in TE, while changes in EO accounted for just 4 kcal/d/y. Between 1994-98 and 2003-06 changes in EO accounted for 39 kcal/d/y of increase and changes in PS accounted for 1 kcal/d/y of decline in the annualized change in TE. While all three components have contributed to some extent to 30-y changes in TE, changes in EO and PS have accounted for most of the change. These findings suggest a new focus for efforts to reduce energy imbalances in US adults.
Highlights
In the context of the growing obesity epidemic [1], it has been suggested that increases in caloric availability and energy intake [2], irrespective of changes in physical activity, are enough to explain the observed increases in weight at the population level [3]
While all three components have contributed to some extent to 30-y changes in total energy (TE), changes in eating/drinking occasions (EOs) and portion size (PS) have accounted for most of the change
Taken together these findings suggest that it is the total meal, not just individual foods consumed, that is important in determining total energy (TE) intake and should be the focus of research
Summary
In the context of the growing obesity epidemic [1], it has been suggested that increases in caloric availability and energy intake [2], irrespective of changes in physical activity, are enough to explain the observed increases in weight at the population level [3]. Theories about the causes of change in energy intake are numerous, but tend to focus on one of three areas: increases in the frequency of eating/drinking occasions (EOs) [4,5,6], especially snacking [7]; increases in the typical portion sizes (PSs) of foods and beverages [8,9,10,11]; or changes in the energy density (ED) of the foods consumed (termed ‘‘volumetrics’’ by Rolls and colleagues) [12,13,14]. People become unhealthily fat by consuming food and drink that contains more energy (kilocalories, or kcal) than they need for their daily activities. In these circumstances, the body converts the excess energy into fat stores
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