Comparative Impact of Plant-Based Protein and Lean Animal Protein Diets on Insulin Sensitivity in Adults

Abstract

Background: Insulin resistance represents a pivotal metabolic disturbance preceding type 2 diabetes mellitus. Dietary protein source has emerged as a modifiable factor influencing glucose regulation and lipid metabolism. While plant-based proteins are increasingly promoted for cardiometabolic benefits, their direct comparative effect on insulin sensitivity relative to lean animal proteins remains underexplored.

Objective: To evaluate whether a plant-based protein diet improves insulin sensitivity more effectively than a lean animal protein diet in adults at risk for type 2 diabetes.

Methods: A 12-week randomized controlled trial was conducted among 100 adults aged 30–55 years with prediabetes in South Punjab. Participants were randomly assigned to receive either a plant-based protein diet or a lean animal protein diet, both isocaloric and matched for macronutrient distribution. Primary outcomes included changes in insulin sensitivity assessed through HOMA-IR, while secondary measures encompassed fasting glucose, HbA1c, lipid profile, body weight, BMI, and waist circumference. Data were analyzed using SPSS version 26, with between-group comparisons performed via independent t-tests and repeated measures ANOVA, assuming normal distribution.

Results: The plant-based group demonstrated a greater reduction in HOMA-IR (−0.7 vs −0.2, p = 0.02) and fasting glucose (−9.2 mg/dL vs −3.3 mg/dL, p = 0.01) compared to the lean animal protein group. Total cholesterol and LDL decreased significantly more in the plant-based group (p ≤ 0.02 for both), alongside a modest increase in HDL (p = 0.04). Body weight and waist circumference also declined more markedly among those consuming plant-derived proteins (p ≤ 0.04).

Conclusion: In adults with prediabetes, a plant-based protein diet led to superior improvements in insulin sensitivity, lipid metabolism, and adiposity reduction compared with an isocaloric lean animal protein diet. These findings support the role of plant-based protein as an effective dietary strategy for mitigating insulin resistance and improving metabolic health.