Substitution or Addition? How Overweight and Obese Adults Incorporate Vegetables into Their Diet During a Randomized Controlled Vegetable Feeding Trial
Authors: Jahns Lisa , Conrad Zach , Johnson LuAnn K , Temple Jennifer , Keim Nancy L , Roemmich James N 
Published: November 2023

Objective

When attempting to eat healthier, individuals may add vegetables to their diet (addition) without changing other eating behaviors. Alternatively, individuals adding vegetables may decrease consumption of other foods (substitution). Distinguishing between the two means of incorporation of vegetables into the diet has implications for behavior change interventions.

Methods

This abstract reports preliminary data from the intervention arm of an 8‐week, randomized, controlled, community‐based feeding study with an 8‐week follow‐up. One of the study aims is to determine whether adding vegetables to the diet results in participants substituting low‐energy‐dense vegetables for energy‐dense foods, or whether energy‐dense food consumption is maintained and is independent of changes in vegetable consumption. For 8 weeks intervention participants were provided minimally‐processed, washed, cut, packed servings of vegetables. The vegetables provided ~300 kcals/day. Participants chose vegetables within each category of the Dietary Guidelines for Americans recommendations but were required to choose amounts for their energy needs. Participants were not told how to incorporate the vegetables into their diet, only that they must eat all vegetables given to them. Substitution was measured in two ways: 1) by 3 baseline 24‐hr recalls using the Automated Self‐Administered 24‐hour Recall and 3 recalls during each 4‐week period, and 2) by self‐report using a consumption log. Daily intakes of energy and food groups were compared using a mixed linear model with Tukey's contrasts for pairwise comparison of means.

Results

The 14 intervention participants to date were 86% female, with mean age and BMI of 37.9 ± 12.8y and 36.7 ± 9.1 kg/m2, respectively. There was no difference in reported energy intake between baseline (2043 ± 235 kcal (SE)) and intervention (1944 ± 177 kcal; P=0.80). Participants reported consuming more vegetables (3.7 ± 0.3 vs 1.4 ± 0.2 servings; P<0.001) and legumes (1.25 ± 0.24 vs 0.20 ± 0.08 P<0.001) and less of the meat, poultry and shellfish group (2.7 ± 0.3 vs 4.3 ± 0.8 servings, P=0.05) during the intervention compared to baseline. There was no change in reported intake of fruits (P=0.95), grains (P=0.55), dairy (P=0.98), oils (P=0.72), added sugars (P=0.93), and solid fats (P=0.31). Participants reported consuming 265 ± 21 kcal in vegetables and 56 ± 12 kcal from legumes per day during the intervention, an increase of 126 ± 31 kcal and 38 ± 14 kcal, respectively, from baseline (P<0.05). Participants self‐reported substituting vegetables for other food groups 29% of the time. The most often‐reported food groupings that vegetables were substituted for were main dishes (37%) and snack foods (24%).

Conclusions

Emphasis should be placed on encouraging people to substitute vegetables for energy‐dense foods that should be consumed in moderation, such as those high in solid fats, added sugars, and refined grains.

Support or Funding Information

USDA‐ARS 3062‐51000‐051‐00D