Insulin resistance in type 2 diabetes can cause the body to break down fat and muscle for energy, leading to weight loss despite increased food intake.

When cells resist insulin, glucose stays in the bloodstream instead of being taken up for energy or storage. The body interprets this as starvation and activates pathways that break down adipose tissue and muscle protein to release fatty acids and amino acids for fuel. This catabolic state can outweigh the caloric surplus from eating more, resulting in net weight loss or stalled gain. Clinical observations note that unintentional weight loss is a common presenting symptom of undiagnosed diabetes.