Inter-related roles of energy intake, energy density, portion size and variety in the prevention of overweight: Implications for environmental change

Gail M. Woodward-Lopez, MPH, RD¹, Lorrene Davis Ritchie, PhD, RD¹, Allen W. Knehans, PhD², Dana E. Gerstein, MPH, RD³, and Patricia B. Crawford, DrPH, RD⁴. (1) Center for Weight and Health, University of California, Berkeley, 3 Giannini Hall, Berkeley, CA 94720-3100, 510-642-1599, gwlopez@nature.berkeley.edu, (2) Department of Nutritional Sciences, Health Sciences Center, The University of Oklahoma, P.O. Box 26901, Oklahoma City, OK 73190, (3) Center for Weight and Health, Unversity of California, Berkeley, 3 Giannini Hall, Berkeley, CA 94720-3100, (4) Department of Nutritional Sciences and Center for Weight and Health, University of California, Berkeley, 9 Morgan Hall, University of California, Berkeley, Berkeley, CA 94720-3104

PURPOSE: Before environmental changes to reduce obesity can be made, the behaviors targeted by these changes must be determined. This session will examine the extent and nature of the evidence supporting a relationship between obesity and the following factors: energy intake, energy density, portion size, and dietary variety.

METHODS: A comprehensive literature review was conducted under the guidance of the Obesity Prevention Network, a network of 6 university Prevention Research Centers. Four lines of evidence were examined: secular trends; experimental studies that elucidate plausible mechanisms of action; observational studies; and prevention trials.

FINDINGS: The literature review revealed both a lack of, and/or serious methodological limitations in, the studies that examined the relationship between these dietary factors and obesity. However, the preponderance of evidence supports the notion that calorie intake has contributed to the recent rise in obesity. Although secular trends and common sense, as well as some experimental studies, support the notion that increases in dietary variety and portion size, of at least some categories of foods, have contributed to obesity, there is too little and/or conflicting evidence in the other categories of evidence to support a firm conclusion. The role of energy density on the other hand is strongly supported by experimental studies, but evidence is weak or non existent in the other categories. Given the absence of scientific support for these factors, which one would logically implicate as contributors to positive energy balance, the dilemma as to whether they should be given priority as a focus for environmental change is discussed.

Learning Objectives:

At the conclusion of the session, the participant will be able to

1) Describe the nature and extent of evidence implicating energy intake, dietary variety, portion size and energy density in the etiology of obesity.
2) Prioritize which of these dietary factors would most appropriately be targeted by efforts to prevent obesity.
3) Describe appropriate environmental changes that are supported by the findings.

Presenting author's disclosure statement:
I do not have any significant financial interest/arrangement or affiliation with any organization/institution whose products or services are being discussed in this session.

Recorded presentation

Environmental Factors and Obesity

The 132nd Annual Meeting (November 6-10, 2004) of APHA