A recent study published in the journal Nutrition and Metabolism sheds light on how the consumption of vegan processed foods may influence weight loss in overweight adults, revealing that reducing animal-based processed foods is key to weight management.
Processed Foods and Weight Gain
A plant-based, low-fat diet is known to offer several health benefits, including weight loss, reduced risk of heart disease, better blood sugar control, and anti-inflammatory properties. However, some plant-derived foods are heavily processed, which can diminish their weight loss potential.
Several studies have highlighted a link between the consumption of ultra-processed foods (UPFs) and an increased risk of weight gain. Despite this, few studies have explored whether this association varies based on whether the processed foods are plant- or animal-based.
About the Study
This study is a secondary analysis of a randomized clinical trial conducted from January 2017 to February 2019. It aimed to explore whether the degree of food processing impacts the effects of a plant-based diet on body weight. The main hypothesis was that plant- and animal-based foods classified under the NOVA food classification system would influence body weight differently.
The study cohort included overweight adults aged 25 to 75 years with a body mass index (BMI) ranging from 28 to 40 kg/m². Participants were excluded if they were smokers, alcohol or drug abusers, diabetic, pregnant, lactating, or already on a vegan diet.
Participants were randomly assigned to either a vegan group or a control group. The vegan group avoided animal products and minimized oil consumption, while the control group did not alter their dietary habits.
Body weight was measured at baseline and after 16 weeks. Foods were categorized by their degree of processing according to the NOVA system: category one (unprocessed or minimally processed), category two (processed ingredients), category three (processed products with added preservatives, salt, and sugar), and category four (ultra-processed foods, or UPFs).
Study Findings
Out of 3,115 participants initially screened by telephone, 244 met the inclusion criteria and were randomly assigned to the vegan or control groups. The vegan group increased their consumption of plant-based foods and decreased their intake of animal products across all NOVA categories.
In category one, the vegan group reduced their consumption of animal foods and increased their intake of plant-based foods. In all other categories, the vegan group decreased their animal food intake compared to the control group. The vegan group also showed a reduction in plant-based food intake, but no significant differences were observed within this group.
When comparing the vegan group to the control group, the vegan group experienced a decrease in body weight. Changes in animal food consumption across all categories were positively associated with weight changes. Multivariable regression models identified the main predictors of weight loss as lower consumption of processed animal foods, reduced intake of unprocessed or minimally processed animal foods, and fewer ultra-processed animal foods.
Reducing the consumption of processed animal foods by 50 g/day was associated with a 1 kg weight loss, even without adjusting for changes in energy intake. A similar weight loss of 1 kg was observed when participants reduced their consumption of unprocessed or minimally processed animal foods by 93 g/day. Furthermore, reducing ultra-processed animal foods by 120 g/day was also independently associated with a 1 kg weight loss.
No significant associations were found between changes in BMI and the ratio of category four (ultra-processed foods) to category one (unprocessed) foods, whether plant- or animal-based.
Key Takeaways
The study concluded that minimizing the consumption of animal-based foods and replacing them with low-fat, plant-derived alternatives—regardless of their level of processing—was associated with clinically significant weight loss. The findings underscore the importance of cutting back on animal-based processed foods to promote weight management.
Strengths and Limitations
A key strength of this study is the inclusion of a control group, which was exposed to the same seasonal variations as the vegan group, ensuring that external factors did not skew the results.
However, the study had some limitations. The reliance on self-reported diet records to assess daily dietary habits could introduce reporting bias. Additionally, the cohort may not be representative of the general population, limiting the generalizability of the findings.
Overall, the study highlights the critical role of reducing animal-based processed foods for effective weight loss, while also supporting the health benefits of plant-based diets.
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