Replacing animal products with plant-based foods linked to weight loss, study finds

A recent study published in Nutrition & Metabolism has found that swapping animal products for plant-based foods, regardless of how processed they are, can result in significant weight loss. The study, conducted by the Physicians Committee for Responsible Medicine, suggests that a diet emphasizing plant-based alternatives – including processed options like soy milk, vegan meat, and dairy substitutes – can positively impact both weight and metabolism.

“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," said Dr Hana Kahleova, director of clinical research at the Physicians Committee for Responsible Medicine. "Filling your plate with plant-based foods – even if they are considered ultra-processed – can have a positive impact on your weight and overall health."

The research was based on a 16-week randomized trial involving participants who were overweight. They were divided into two groups: one following a low-fat, plant-based diet with no calorie restrictions, and another control group that made no dietary changes. The results showed that those in the plant-based diet group experienced an average weight loss of 13 lbs (5.9kg), an increase in metabolism and energy expenditure after meals, and improvements in cardiometabolic risk factors compared to the control group.

The study also examined how processed foods factored into the weight loss. Participants’ food intake was categorized using the NOVA classification system, which ranks foods based on their level of processing. NOVA category 1 includes unprocessed or minimally processed foods, while category 2 consists of processed ingredients such as salt, sugar, and oil. Category 3 includes processed foods made with added preservatives, while category 4 is composed of ultra-processed foods that undergo industrial modifications.

Participants in the plant-based group increased their intake of plant-based foods across all four NOVA categories while significantly reducing their consumption of animal-based products. The strongest predictors of weight loss were reductions in processed animal foods such as smoked fish, unprocessed or minimally processed animal products such as milk, beef, and eggs, and ultra-processed animal foods such as cheese, fried chicken, and sausage.

The weight loss was primarily attributed to a reduction in calorie and fat intake, an increase in dietary fiber, and higher post-meal calorie burn due to an improved metabolism.

One of the most notable takeaways from the study was the role of processed plant-based foods in weight loss. Many discussions on diet and health focus on minimizing processed foods, but this study suggests that even processed plant-based options – such as canned beans, breakfast cereals, and veggie burgers – can be part of a healthy diet.

"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," said Dr Kahleova.

With rising rates of obesity, diabetes, and cardiovascular disease, the findings of this study highlight the potential benefits of shifting toward plant-based diets, even when convenience foods are included. The study reinforces the idea that reducing animal product consumption – especially highly processed options like cheese and fried meats – can have measurable health benefits.

While some nutrition experts argue that avoiding processed foods entirely is the best strategy for health, this research suggests that plant-based convenience foods can still be part of a weight-loss-friendly diet. The findings contribute to the growing body of evidence supporting plant-based nutrition as a way to improve metabolic health, reduce the risk of chronic diseases, and promote sustainable dietary habits.