Dietary energy density in the treatment of obesity: a year-long trial comparing 2 weight-loss diets

Abstract

Background: Consuming foods low in energy density (kcal/g) decreases energy intake over several days, but the effectiveness of this strategy for weight loss has not been tested.

Objective: The effects on weight loss of 2 strategies for reducing the energy density of the diet were compared over 1 y.

Design: Obese women (n = 97) were randomly assigned to groups counseled either to reduce their fat intake (RF group) or to reduce their fat intake and increase their intake of water-rich foods, particularly fruit and vegetables (RF+FV group). No goals for energy or fat intake were assigned; the subjects were instructed to eat ad libitum amounts of food while following the principles of their diet.

Results: After 1 y, study completers (n = 71) in both groups had significant decreases in body weight (P < 0.0001). Subjects in the RF+FV group, however, had a significantly different pattern of weight loss (P = 0.002) than did subjects in the RF group. After 1 y, the RF+FV group lost 7.9 +/- 0.9 kg and the RF group lost 6.4 +/- 0.9 kg. Analysis of all randomly assigned subjects also showed a different pattern of weight loss between groups (P = 0.021). Diet records indicated that both groups had similar reductions in fat intake. The RF+FV group, however, had a lower dietary energy density than did the RF group (P = 0.019) as the result of consuming a greater weight of food (P = 0.025), especially fruit and vegetables (P = 0.037). The RF+FV group also reported less hunger (P = 0.003).

Conclusion: Reducing dietary energy density, particularly by combining increased fruit and vegetable intakes with decreased fat intake, is an effective strategy for managing body weight while controlling hunger.

Conflict of interest statement

None of the authors had any conflicts of interest.

Figures

FIGURE 1

Flow diagram of subject enrollment, random assignment, and completion of the study protocol.

FIGURE 2

Mean (± SEM) change in body weight for study completers in the reduced-fat (RF) and reduced-fat plus increased fruit and vegetable (RF+FV) intervention groups over time. Random coefficients analysis was used to model the longitudinal response over time, with control for baseline values. The group × time interaction (P = 0.002) indicates that the response over time differed between the groups. The interaction remained significant (P = 0.021) when all randomly assigned subjects were included in the analysis. Baseline values did not differ significantly between the groups (unpaired t test).

FIGURE 3

Mean (± SEM) food energy density (kcal/g) for study completers in the reduced-fat (RF) and reduced-fat plus increased fruit and vegetable (RF+FV) intervention groups over time. Differences in dietary energy density between the groups were determined from a mixed linear model with repeated measures, by using all available time points and with control for baseline values. The group × time interaction was significant (P = 0.019), which indicated that dietary energy density was significantly less in the RF+FV group than in the RF group during the intervention. Baseline values did not differ significantly between the groups (unpaired t test).