Effect of Changes in the Intake of Weight of Specific Food Groups on Successful Body Weight Loss during a Multi–Dietary Strategy Intervention Trial

Abstract

Background: Distinct weight loss dietary strategies are associated with changes in specific food groups.

Objective: To address the effect of changes in specific weight of food groups on weight loss in a 2-year low-fat, Mediterranean, low-carbohydrate intervention trial (DIRECT).

Methods: We assessed changes in the intake of 12 food groups among 322 participants (body mass index [BMI] = 31 kg/m²; age = 52 years; 86% men), using a validated electronic food frequency questionnaire.

Results: The weight of the 3592.9 ± 1558 (g/d ± SD) of baseline food consumed consisted mainly of liquids, excluding water (32.6% of total weight of food); vegetables (18.8%), fruits (17.7%), dairy (9.0%), meat (7.7%), and bread/cereal/pasta/potatoes (7.1%). Participants significantly reduced food intake by 283.73 ± 1342 (g/d ± SD) at 6 months and by 963.36 ± 1869 (g/d ± SD) at 24 months (p < 0.05 as compared with baseline). Food weight changes were similar across diet groups (p = 0.366), whereas 6-month body weight loss was −4.6 ± 4.4 kg, −4.7 ± 4.9 kg, and −6.4 ± 6.6 kg for low-fat, Mediterranean, and low-carbohydrate groups, respectively; p < 0.026). In multivariate regression models, adjusted for age, sex, baseline body weight, and changes in weight intake of 12 food groups (g/d), independent dietary predictors (standardized-β) at 6 months (rapid weight loss phase) were as follows: decreased consumption of sweets and cakes (β = 0.493; p = 0.008) in the low-fat group, tendency toward increased crude legumes (β = −0.196; p = 0.061) in the Mediterranean group, and increased vegetable intake (β = −0.249; p = 0.018) in the low-carbohydrate diet group. In the entire group, in models further adjusted for diet type, leading predictors for rapid weight loss phase were as follows: increased vegetables by ∼140 g/d (β = −0.116; p = 0.045) and decreased intake of sweets and cakes by ∼30 g/d (β = 0.162; p = 0.010). Universal predictors for 2-year successful weight loss in the entire group were as follows: increased intake of vegetables (β = −0.192; p = 0.007) and meat (β = −0.146; p = 0.026) and decreased intake of eggs (β = 0.187; p = 0.003), processed legumes (β = 0.195; p = 0.002), and beverages (β = 0.135; p = 0.032).

Conclusions: Two-year weight loss is associated with a decrease of ∼1 kg of total food consumed and may be achieved by a variety of changes in specific food groups within different diet strategies. Universal predictors of successful weight loss in the rapid weight loss phase across all diet strategies are increasing the weight of intake of vegetables and decreasing the weight of intake of sweets and cakes.

Key words::

• food groups
• food frequency questionnaire
• weight loss
• low-fat diet
• Mediterranean diet
• low-carbohydrate diet

ACKNOWLEDGMENTS

We are thankful to the 322 DIRECT participants for their consistent cooperation. We are indebted to the members of the DIRECT steering committee: Prof Shimon Weitzman, Prof Uri Goldbourt, and Prof Eran Leitersdorf.

Fig. 1. Total weight of food intake (g/d ± SE) at baseline and at 6 and 24 months across dietary intervention groups.*

* Tested with analysis of variance (ANOVA) for between-group differences, and with paired Student t-tests for within-group comparisons. All diet groups reduced their food intake significantly from baseline to 6 and 24 months (within groups, p < 0.005). No significant differences were observed between diet groups. Vertical bars indicate standard errors.

Fig. 2a. Leading, moderate, and minor absolute changes in the weight of intake of specific food groups (g/d ± SE) at 6 months across diet groups.*

* p values represent significant differences between Mediterranean or low-carbohydrate diet groups and low-fat diet groups, as tested with ANOVA.

¹ The difference between low-carbohydrate and low-fat groups in terms of changes in intake of breads, cereals, potatoes, and pasta (p = 0.001).

² The difference between Mediterranean and low-fat groups in terms of changes in fish intake (p = 0.020).

³ The difference between low-carbohydrate and low-fat groups in terms of changes in egg intake (p = 0.013).

⁴ The difference between low-carbohydrate and low-fat groups in terms of changes in intake of oils and fats (p < 0.001).

⁵ The difference between Mediterranean and low-fat groups in terms of changes in intake of crude legumes (p < 0.001).

Fig. 2b. Leading, moderate, and minor absolute changes in the weight of intake of specific food groups (g/d ± SE) at 24 months across diet groups.*

* p values represent significant differences between the Mediterranean or low-carbohydrate diet group and the low-fat diet group, tested with ANOVA.

¹ The difference between low-carbohydrate and low-fat groups in terms of changes in intake of breads, cereals, potatoes, and pasta (p = 0.038).

² The difference between low-carbohydrate and low-fat groups in terms of changes in take of oils and fats (p = 0.001).

Table 1. Baseline Demographic Characteristics and Mean Weight and Energy Content and Proportion of Total Intake of Food and Intake of the 12 Food Groups*

Table 2. Prediction of 6 Months Weight Loss (kg) by Changes (delta) in the Weight of Intake of Food Groups (g/d); Multivariate Model*^†‡

Table 3. Prediction of 24-Month Weight Loss (kg) by Changes (delta) in the Weight of Intake of Food Groups (g/d); Multivariate Model*^†‡

Appendix 1. Food Items in Each Food Group

Notes

Ethical approval statement: The present study was approved by the local Institutional Ethical Board, and was carried out in compliance with the Health Insurance Portability and Accountability Act (HIPAA) guidelines. It was then registered at the clinical trials site: ClinicalTrials.gov number, NCT00160108.

*Both authors equally contributed to this paper.

All authors read and approved the final manuscript.

None of the authors have relationships with companies that make products relevant to the manuscript.

Funding sources: The study was funded by the following sources: (1) The Israeli Ministry of Health, Chief Scientist Office; (2) The Dr. Robert C. and Veronica Atkins Research Foundation. This foundation was not involved in any stage of the design, conduct, or analysis of the study and had no access to the study results before publication.