Swapping animal products for plant-based foods may help you lose weight. (© ChayTee – stock.adobe.com)
In a nutshell
- A new study found that while processed animal foods are linked to weight gain, processed plant-based foods did not show the same effect.
- Swapping animal products for plant-based foods leads to weight loss. Participants on a low-fat vegan diet lost an average of 13 pounds in 16 weeks, even when consuming processed plant foods like veggie burgers and soy milk.
- Food source matters more than processing level. The study suggests that reducing animal foods, whether processed or not, was the biggest factor in weight loss.
WASHINGTON — Health experts have hammered home that processed foods lead to weight gain. But what if that’s not entirely true? Researchers from the Physicians Committee for Responsible Medicine have uncovered a dietary loophole that could make healthy eating significantly more accessible: processed foods from plants don’t appear to impact weight gain like processed animal products do.
“Our research shows that choosing a bagel instead of bacon for breakfast or a veggie burger instead of a hamburger for dinner is the best option if you are looking to lose weight,” says Dr. Hana Kahleova, Ph.D., director of clinical research for the Physicians Committee for Responsible Medicine, in a statement.
Published in Nutrition & Metabolism, this research challenges long-held beliefs about processed foods and weight gain. You can enjoy those packaged veggie burgers and still shed pounds. The key is cutting out animal products altogether.
“Filling your plate with plant-based foods—even if they are considered ultra-processed like soy milk and vegan meat and yogurt alternatives—instead of animal products can have a positive impact on your weight and overall health,” says Dr. Kahleova.
This finding could be a game-changer for people who want to try plant-based eating but worry about having to cook everything from scratch. It could also help combat the rising tide of diet-related diseases in America.
The Food Origin Matters More Than Processing Level
Researchers analyzed data from a clinical trial examining how a low-fat vegan diet affects body weight. They split 244 overweight adults into two groups: one followed a vegan diet, while the control group kept eating their usual meals for 16 weeks.
The vegan group received weekly classes and instructions to avoid animal products and use minimal oils, but they had no calorie limits. They weren’t told to avoid processed foods. Frozen vegan pizzas and plant-based burgers were fine, as long as they contained no animal ingredients.
After 16 weeks, the numbers told a clear story. The vegan group dropped an average of 13 pounds (5.9 kilograms) more than the control group, despite many of them eating processed plant foods.
Using the NOVA food classification system (which ranks foods from minimally processed to ultra-processed), researchers found that reducing animal food consumption was correlated with greater weight loss across all levels of processing.
The biggest weight loss predictors were:
- Eating less processed animal foods (like smoked fish)
- Cutting back on unprocessed animal foods (like milk, beef, and eggs)
- Reducing ultra-processed animal foods (like cheese, fried chicken, and sausage)
Surprisingly, no category of plant-based processed foods showed any meaningful connection to weight gain—not even the ultra-processed options.
How Plant-Based Foods Help With Weight Loss
Plant foods pack more fiber and less fat than animal products, helping people feel satisfied with fewer calories. The researchers found that participants lost weight from eating fewer calories and less fat, consuming more fiber, and burning more calories through improved metabolism after meals. The vegan group consumed fewer calories on average, despite having no set calorie restrictions.
“Our new study is an important reminder that plant-based foods that are considered processed, like canned beans, cereal, and veggie burgers, are actually part of a healthy diet that can help fight America’s diet-related chronic disease epidemics,” says Dr. Kahleova.
This doesn’t mean all boxed and packaged plant foods count as healthy foods. Other factors like nutrient content and effects on gut health matter too. But for weight management specifically, switching to plant-based options works, even if they come in packages.
Making Plant-Based Eating More Doable
This makes plant-based diets more approachable for those who may be hesitant to fully dive into making vegan meals from scratch. Newcomers can rely on convenient processed plant alternatives while they get comfortable with the lifestyle.
Plant-based diets help with more than just weight loss; they’re linked to better heart health and improved blood sugar control. But this study specifically shows their effectiveness for dropping pounds, regardless of processing level.
What matters isn’t how much your food has been tinkered with, but whether it began as a plant or an animal. This distinction could be the secret weapon for anyone who’s tried and failed at diets that demonize all convenience foods. So go ahead, reach for that packaged veggie burger or plant-based frozen meal. Your busy schedule, your waistline, and maybe even the planet will thank you.
Paper Summary
Methodology
Researchers performed a secondary analysis of data from a randomized clinical trial examining the effects of a low-fat vegan diet. They analyzed three-day food records from 244 overweight adults (BMI between 28-40) who were randomly assigned to either a vegan diet or control group for 16 weeks. All foods were categorized using the NOVA classification system, which sorts foods into four categories based on processing level, from minimally processed (category 1) to ultra-processed (category 4). Foods were further classified by whether they came from animal or plant sources.
Results
The vegan group lost significantly more weight than the control group—13 pounds (5.9 kg) more on average. Changes in animal food consumption across all processing categories positively correlated with body weight changes, meaning that reducing animal foods led to weight loss. The top three independent predictors of weight loss were reduced intake of processed animal foods, unprocessed/minimally processed animal foods, and ultra-processed animal foods. Notably, no category of plant-based foods showed a significant positive correlation with weight gain, regardless of processing level.
Limitations
The study relied on self-reported dietary records, which can contain inaccuracies. The study population consisted of volunteers willing to try a vegan diet, who might not represent the general population and may have been more motivated than average. The 16-week duration, while substantial for a dietary intervention, doesn’t show long-term effects. Finally, the study focused specifically on weight loss and didn’t examine other health outcomes that might be affected differently by processed foods.
Discussion and Takeaways
This research challenges the common narrative that all processed foods lead to weight gain, suggesting instead that the source of food (animal versus plant) may be more important than its degree of processing for weight management. For practical purposes, these findings make plant-based diets more approachable and sustainable, as people can include convenient processed options without derailing weight loss efforts. While whole, minimally processed foods remain ideal for overall health, the flexibility to include some processed plant foods may help more people successfully transition to and maintain a plant-based diet.
Funding and Disclosures
This research was funded by the Physicians Committee for Responsible Medicine, a nonprofit organization that promotes plant-based nutrition. Several study authors, including lead author Dr. Kahleova, received compensation from this organization for their work on the study. Dr. Barnard, another author, serves without compensation as president of the Physicians Committee for Responsible Medicine and Barnard Medical Center, and receives royalties and honoraria from books, articles, and lectures related to nutrition.
Publication Information
The study, titled “Vegan diet, processed foods, and body weight: a secondary analysis of a randomized clinical trial,” was published in Nutrition & Metabolism in 2025 (Volume 22, Issue 21). The research was conducted between January 2017 and February 2019 in Washington, DC, and was registered on ClinicalTrials.gov (NCT02939638).
