How does a plant-based diet affect body weight?

In a recent study published in European Journal of Clinical NutritionResearchers analyzed randomized controlled trial (RCT) data to determine the association between plant-based dietary index (PDI), unhealthy PDI (uPDI) and healthy PDI (hPDI) and weight loss among overweight adults.

Study: Does food quality matter? Secondary analysis of a randomized clinical trial. Image credit: Wild As Light/Shutterstock.com

Background

A plant-based diet is linked to lower weight and improved health outcomes. A prospective cohort study conducted in the United States (US) in 2021 showed that increasing PDI and hPDI were associated with a lower risk of type 2 diabetes. However, uPDI modifications did not occur.

The findings were confirmed by serum metabolite analysis. Observational studies have been proposed to measure the nutritional value of plant-based food consumption patterns resulting in the formulation of PDI, uPDI and hPDI indices.

However, the relationship between such classification and body weight needs to be confirmed by randomized controlled trials.

About the study

In the present study, researchers evaluated the relationship between changes in body weight and changes in three PDI indices following a vegan diet.

The primary RCT was conducted from January 2017 to February 2019 in Washington, District of Columbia. The secondary study included 244 individuals randomized to the vegan diet group (intervention, n = 122) or the control group (n = 122) for 16 weeks. .

The intervention group followed a diet low in fat and high in vegetables, fruits, legumes, and whole grains, while the controls did not make any dietary changes. Registered dietitians analyzed three days of food records (one weekend and two weekdays) to calculate the PDI, uPDI, and hPDI indices.

A repeated measures analysis of variance (ANOVA) was performed to analyze the statistical data. Multiple regression modeling was performed with all dietary components as candidate estimators to identify dietary components that independently predicted changes in body weight.

Individual food components investigated include fruits, vegetables, grains, nuts, legumes, vegetable oils, tea and coffee, fruit juices, sugary beverages, refined grains, potatoes, sweets, animal fats, milk , eggs, animal-based products, meat, and seafood.

results

Overall, 223 (91%) individuals completed the study. Self-reported caloric intake was significantly reduced in both study groups, especially among those following a vegan diet (368 kcal/day reduction). Macronutrient percentages did not change significantly between controls.

In contrast, in the intervention group, individuals increased their intake of carbohydrates (23% increase in daily calories) and fiber (12 g/day increase) and decreased fat (18% reduction in daily calories), protein (5.0% reduction). significantly increased. daily calories), and cholesterol (215 mg/day reduction).

Over 16 weeks, intake of fruits, vegetables, whole grains, legumes, fruit juices, animal fats, milk, eggs, meat, and seafood increased by 0.8 points among participants on a vegan diet. , increased by 1.2 points. 1.6 points, 0.4 points, 1.6 points, 1.9 points, 1.8 points, 1.9 points and 1.5 points respectively.

Conversely, consumption of nuts, vegetable oils, tea and coffee, sugary beverages, refined grains and sweets decreased by 0.8 points, 1.3 points, 0.2 points, 0.5 points, 1.3 points and 0.1 points respectively. points, respectively.

Body weight was significantly reduced in the intervention group (a reduction of 5.9 kg) due to a reduction in visceral fat (209 cm3 reduction) and fat mass (4.1 kg reduction).

All three PDI indices were significantly elevated in the intervention group with effect sizes of 11, 11, and 5.4 for PDI, hPDI, and uPDI, respectively. Changes in all PDI indices were significantly associated with changes in body weight.

Multiple regression modeling showed that dietary components independently predicting weight loss included whole grains, legumes, meat, vegetable oils, and sweets. Consumption of vegetables, fruits, whole grains, legumes, fruit juice, and potatoes was negatively associated with weight change.

Conversely, consumption of nuts, vegetable oils, tea and coffee, sugar-sweetened beverages, refined grains, sweets, animal fats, milk, eggs, meat and seafood was positively associated with weight changes.

Indications

Overall, study findings indicate inverse relationships between plant-based dietary indices and body weight changes.

Findings show that reducing consumption of animal-based products, vegetable oils, refined grains, sweets, tea and coffee, meat, seafood, eggs and dairy products can lead to weight loss in overweight adults.

Weight loss strategies should aim to increase dietary components such as vegetables, fruits, legumes and whole grains.

The findings may help weight management programs and reduce the health burden of obesity. However, further research, including randomized controlled trials with more diverse populations, is needed to increase the generalizability of study findings.

Future studies should include objective measures of dietary data collection to improve standardization of outcomes.