Plenary Lecture 1: Dietary strategies for the prevention and treatment of obesity

Abstract

Obesity is a rapidly-growing public health problem that is related in part to the foods available in the eating environment. Properties of foods such as portion size and energy density (kJ/g) have robust effects on energy intake; large portions of energy-dense foods promote excess consumption and this effect starts in early childhood. Studies show, however, that in both adults and children these food characteristics can also be used strategically to moderate energy intake, as well as to improve diet quality. Dietary energy density can be reduced by increasing intake of water-rich foods such as vegetables and fruits. Their high water content allows individuals to eat satisfying portions of food while decreasing energy intake. Filling up at the start of a meal with vegetables or fruit and increasing the proportion of vegetables in a main course have been found to control hunger and moderate energy intake. Data from several clinical trials have also demonstrated that reducing dietary energy density by the addition of water-rich foods is associated with substantial weight loss even though participants eat greater amounts of food. Population-based assessments indicate that beginning in childhood there is a relationship between consuming large portions of energy-dense foods and obesity. These data suggest that the promotion of diets that are reduced in energy density should be an important component of future efforts to both prevent and treat obesity.

Fig. 1

Daily energy intake for ten women (○, ●) and thirteen men (△, ▲) who were served baseline (100%; ○, △) and large (150%; ●, ▲) portions of all foods over 11 d. Values are means with their standard errors represented by vertical bars. Serving large portion sizes led to a significant increase in daily energy intake (P<0.0001), which did not differ by participant gender and showed no evidence of change over time. (From Rolls et al.(17); reprinted with permission from Macmillan Publishers Ltd; copyright 2007.)

Fig. 2

Cumulative food and beverage intake (A) and energy intake (B) over 2 d in twenty-six preschool-age children who were served foods and beverages that were reduced in energy density at breakfast, lunch, and afternoon snack. Dinner and evening snack were not varied in energy density (↓). (•–•), Higher energy density; (○- -○) lower energy density. Values are means with their standard errors represented by vertical bars. There was no effect of energy density on the cumulative weight of food and beverages consumed over 2 d. There was a significant effect of energy density on cumulative energy intake starting at breakfast on day 1 and accumulating over the course of 2 d, as assessed by a mixed linear model (P<0.01). (From Leahy et al.(52); reproduced with permission from the American Journal of Clinical Nutrition.)

Fig. 3

Cumulative energy intakes by meal for twenty-four women who were served 2 d menus that were varied in energy density (ED; △, ▲, 100%; ○, ●, 75%) and portion size (▲, ●, 100%; △, ○, 75%). Values are means with their standard errors represented by vertical bars. All means at a given time point were significantly different (P ≤ 0.003). Data were analysed using a mixed linear model with repeated measures. (From Rolls et al.(14); reproduced with permission from the American Journal of Clinical Nutrition.)

Fig. 4

Change in body weight over time for seventy-one obese women who completed a 1-year weight-loss trial. Women were randomly assigned to receive either advice to reduce dietary fat (●; n 36) or advice to reduce dietary fat and increase intake of water-rich foods including fruits and vegetables (○; n 35). Advice was provided in individual sessions in the first 6 months and in less-frequent individual and group sessions in the second 6 months. Values are means with their standard errors represented by vertical bars. Random coefficients analysis was used to model the longitudinal response over time, controlling for baseline values. The group × time interaction (P = 0.002) indicates that the response over time differed between the groups. (From Ello Martin et al.(55); reproduced with permission from the American Journal of Clinical Nutrition.)

Fig. 5

Change in daily weight of food consumed (A), daily energy intake (B) and body weight (C) after 6 months in 658 participants in the PREMIER trial. Participants received one of several dietary interventions to reduce blood pressure and were classified into tertiles based on the magnitude of change in dietary energy density after intervention: tertile 1, increase or small decrease ( + 4·6 to − 0·4kJ ( + 1·09 to − 0·10 kcal)/d; ); tertile 2, medium decrease ( − 0·5 to − 2·1kJ ( − 0·11 to − 0·51 kcal)/d; ); tertile 3, large decrease ( − 2·2 to − 9·8kJ ( − 0·52 to − 2·35 kcal)/d; □). Values are means with their standard errors represented by vertical bars. ^x,y,zMeans with unlike superscript letters were significantly different (P<0.05) using ANOVA with a general linear model adjustment for baseline values followed by a Tukey-Kramer adjustment for multiple comparisons. (From Ledikwe et al.(56).)