Physicians Committee study: plant-based swaps help type 1 diabetes patients shed pounds, improve insulin response

Replacing animal products with plant-based foods, even ultra-processed options such as plant milks and meat substitutes, can promote weight loss and improve insulin sensitivity in people with type 1 diabetes, according to new research from the Physicians Committee for Responsible Medicine. The findings, published in the journal Nutrition, Metabolism & Cardiovascular Diseases, offer fresh insight into how diet composition might help manage the chronic condition.

“Choosing a veggie burger instead of a cheeseburger – and other plant-based dietary swaps – can help people with type 1 diabetes who want to lose weight and improve how their body responds to insulin,” commented Hana Kahleova, MD, PhD, lead author of the study and director of clinical research at the Physicians Committee for Responsible Medicine. “The key to success is replacing all animal products with plant-based foods – whether unprocessed fruits and veggies or ultra-processed cereal, plant milks, and meat alternatives.”

The research is based on a secondary analysis of the Physicians Committee’s earlier randomized clinical trial, which was the first of its kind to explore the impact of a vegan diet in adults with type 1 diabetes. Over the course of 12 weeks, 58 participants with type 1 diabetes were randomly assigned to either a low-fat vegan group with no restrictions on calories or carbohydrates, or to a portion-controlled group that reduced daily calorie intake for those who were overweight while maintaining stable carbohydrate consumption.

In this new analysis, researchers wanted to understand whether the level of processing in the foods participants consumed played a role in weight loss and insulin sensitivity improvements. To investigate this, the scientists examined the participants’ dietary records and classified all foods – both animal-based and plant-based – using the NOVA system. This system groups foods according to how much they have been processed. NOVA category 1 includes unprocessed or minimally processed items like fresh fruits and vegetables, grains, and legumes. Category 2 covers processed culinary ingredients, such as oils or sugar. Category 3 includes processed foods such as canned vegetables with added salt or cheese, while category 4 encompasses ultra-processed foods, which are highly engineered and often contain additives or industrially modified ingredients.

Among those following the vegan diet, consumption of animal-derived foods decreased across all NOVA categories. Meanwhile, their intake of unprocessed or minimally processed plant-based foods – classified as NOVA category 1 – rose significantly. These foods included fruits, vegetables, grains, and beans. However, there were no notable shifts in the consumption of plant-based foods in NOVA categories 2, 3, and 4 for either the vegan group or the portion-controlled group.

By the end of the study period, individuals in the vegan group lost an average of 5.2kg (approximately 11lbs). They also experienced improved insulin sensitivity, suggesting that their bodies became more effective at using insulin to manage blood sugar levels. In contrast, participants in the portion-controlled group saw no significant changes in either weight or insulin sensitivity.

Beyond weight and insulin metrics, the original Physicians Committee study also documented other benefits for those following a vegan diet. Participants in the vegan group reduced their overall insulin requirements and experienced improvements in cholesterol profiles and kidney function, markers that are crucial for long-term health in people living with type 1 diabetes.

These findings add to a growing body of research suggesting that plant-based diets can play a beneficial role in managing diabetes, traditionally a disease more commonly associated with insulin resistance and weight concerns in type 2 cases. Yet, even for those with type 1 diabetes, who are dependent on insulin because their bodies do not produce it, dietary changes may help reduce the amount of insulin needed and support better metabolic health overall.

Kahleova emphasized that the improvements observed were not solely tied to the consumption of whole, unprocessed foods. “The key to success is replacing all animal products with plant-based foods – whether unprocessed fruits and veggies or ultra-processed cereal, plant milks, and meat alternatives,” she said.

While many health experts typically caution against overconsumption of ultra-processed foods due to links with obesity and chronic disease, this study suggests that even these foods, when part of a fully plant-based diet, might offer metabolic benefits compared to animal-based products in the context of type 1 diabetes management. However, the researchers noted that further studies would be valuable to clarify the long-term effects of ultra-processed plant-based products.

For individuals with type 1 diabetes, these results may offer a new avenue for improving health outcomes beyond traditional calorie counting or carbohydrate management, highlighting the potential of dietary pattern shifts toward plant-based eating.