Plant-based foods promote weight loss, regardless of processing

Food choices shape our bodies, our health, and even our weight and futures. For decades, the debate over processed foods has been raging – are they the villains behind rising obesity rates, or is the story more complicated? Some argue that any ultra-processed food is bad news, while others say it depends on what’s being processed.

A recent study shakes up the conversation. The research suggests that swapping out animal products for plant-based alternatives – even the ultra-processed ones – can lead to significant weight loss.

Plant-based food and weight gain

Many studies have shown that plant-based diets support weight loss, lower cholesterol, and improve heart health. However, concerns remained about whether consuming processed plant-based foods would hinder these benefits.

Dr. Hana Kahleova, director of clinical research at the Physicians Committee for Responsible Medicine, emphasized the significance of the current study.

“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. Kahleova.

“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.”

Assumptions about processed foods

This research directly challenges the belief that all processed foods contribute to weight gain. While ultra-processed animal products are strongly linked to increased body weight, processed plant-based foods do not appear to have the same negative effect.

To test the effects of a plant-based diet, researchers followed 244 overweight adults over 16 weeks. They split them into two groups. One group switched to a low-fat, plant-based diet with no restrictions on calories.

The other group? They didn’t change anything. No one counted calories or measured portions. The only difference was what they ate.

At the end, the vegan group lost an average of 13 pounds (5.9 kg). Their metabolism sped up. Their overall cardiometabolic health improved. Meanwhile, the control group – those who stuck with their regular diets – saw no significant change.

The NOVA Classification

The NOVA system is a widely recognized method for categorizing foods based on their level of processing. It helps researchers and nutritionists analyze how different types of foods impact health. The system divides foods into four categories.

Category 1: Unprocessed foods

These are foods in their natural state or with minimal alterations. Examples include fresh fruits, vegetables, whole grains, nuts, and legumes.

Any changes made to these foods – such as drying, freezing, or grinding – are only done to make them easier to store or prepare, without significantly altering their nutritional value.

Category 2: Processed ingredients

This category includes substances extracted from natural foods, such as salt, sugar, and vegetable oils. These ingredients are typically used to season or cook other foods but are not consumed on their own in significant amounts.

While they are not harmful in moderation, excessive intake – especially in the form of added sugar and refined oils – can contribute to health issues like obesity and heart disease.

Category 3: Processed foods

Processed foods are made by combining unprocessed foods (Category 1) with processed ingredients (Category 2). These include foods like canned vegetables with added salt, fresh bread, cheese, and smoked fish.

Processing in this category aims to enhance taste, texture, or shelf life without fundamentally changing the food’s natural composition.

Category 4: Ultra-processed foods

These foods undergo extensive industrial processing, often containing artificial additives, preservatives, and ingredients not typically found in a home kitchen.

Examples include packaged snacks, soft drinks, instant noodles, frozen meals, and processed meats like hot dogs and sausages.

Ultra-processed foods are designed for convenience and long shelf life but often contain high levels of unhealthy fats, sugars, and additives that may contribute to weight gain and chronic diseases.

Targeting all four categories

Participants in the vegan group reduced their intake of animal products across all four NOVA categories while increasing their consumption of plant-based foods.

This shift contributed to their weight loss, suggesting that the reduction in animal-based foods played a bigger role than the level of processing of plant-based foods.

Food factors driving weight loss

So what exactly caused the weight loss? The researchers identified three major shifts that made the difference. First, as discussed above, participants who lost weight significantly cut back on processed animal products – things like smoked meats and processed cheese.

Second, they ate fewer unprocessed or minimally processed animal foods, such as milk, eggs, and lean meats. Finally, they dramatically reduced ultra-processed animal foods like fried chicken, sausage, and packaged dairy products.

The data showed that for every 50 grams per day reduction in processed animal food, participants lost about one kilogram (2.2 pounds) over the course of the study. The effect was even more pronounced with unprocessed animal foods – cutting 93 grams per day resulted in a kilogram of weight loss.

But the biggest impact? Ultra-processed animal foods. Reducing them by 120 grams daily led to a kilogram of weight loss in just 16 weeks.

Plant-based processed foods

One of the most striking findings was that processed plant-based foods did not contribute to weight gain.

Unlike animal-based ultra-processed foods, plant-based versions such as soy milk, veggie burgers, and cereal did not have a significant association with increased body weight.

“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.

Plant foods support weight loss

A plant-based diet helps with weight loss in several ways. It is lower in fat and calories than diets with animal foods. High fiber content makes people feel full longer, so they eat less.

It also boosts metabolism. Vegan participants burned more calories after eating than those who ate animal foods. This helped them manage their weight.

Fiber is another key factor. It improves digestion, supports gut health, and reduces calorie absorption. Eating more fiber helps control appetite and maintain a healthy weight.

However, it is important o note that the study also had some limitations. Dietary intake was self-reported, which could introduce errors in food tracking. The participants were volunteers, meaning they may have been more motivated than the general population to follow dietary changes.

Additionally, the study only lasted 16 weeks, and long-term effects still need further investigation.

What this means for diet and health

The takeaway from this research is simple. Cutting animal products – whether you replace them with whole foods or processed plant-based alternatives – leads to weight loss.

For those looking to manage their weight, this suggests that focusing on food origin might be more important than avoiding all processed foods.

Choosing plant-based versions of familiar foods doesn’t just make the transition easier – it also supports better health outcomes.

The study is published in the journal Nutrition & Metabolism.

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