Energy Intake

Analysis of the dietary factors associated with obesity is confounded by the difficulties in assessing food intake and eating behaviour. Dietary surveys are increasingly beset by the problem of underreporting, probably related to the increased awareness of nutrition issues and concern over body weight, which leads individuals to consciously or sub-consciously mis-report their food intake.

In 1986 Prentice et al. demonstrated that obese women under-reported energy intake relative to energy needs by a mean of 3.5MJ/day, while among lean women the two measures agreed to within 0.14 MJ/day (Prentice et al., 1986). This observation has been repeatedly reconfirmed, although it is now recognized that there is a spectrum of mis-reporting of food intake across the population, the nature of which is not easily predicted on the basis of individual phenotype or demographic statistics. Others may alter their dietary habits during periods of food recording, usually leading to a record of undereating (Goris et al., 2000)

Analysis of the dietary determinants of obesity is also confounded by the problems of post-hoc changes in consumption in response to increasing body weight. This makes it difficult to draw quantitative conclusions from crosssectional or even prospective studies of food intake and body weight. Nonetheless increasingly refined recording tools and statistical analysis are seeking to understand more about the broader context of eating behaviour with targeted questions about the location and social context of eating episodes and using factor analysis to identify types of dietary patterns, which may inform future strategies to prevent and treat obesity (Whichelow and Prevost, 1996).

Instead much of our understanding of the relationship between dietary factors and the risk of obesity comes from experimental studies in the laboratory or highly controlled intervention studies in the community. These may not truly mimic eating behaviour in a naturalistic setting, but they provide useful insights into the response to imposed dietary manipulations under standardized conditions.
(Written By: Susan A. Jebb and Jeremy Krebs in The Book Of Obesity And Diabets)