Why does diabetes cause unexplained weight loss?

In a new case...: In a brand new case of diabetes, especially type 1, people experience excessive thirst, excessive hunger, and excessive urination. Their blood sugar is high, and they "spill" this sugar into the urine. The weight loss can be attributed to this calorie loss, but also to volume depletion, i.e., dehydration. Most type 2 diabetics present more gradually, and will typically be overweight or obese.

Lack of Insulin: People with diabetes can't convert sugar and starches found in foods into energy. Extra sugar either builds up in the bloodstream or passes out in the urine. People begin to lose weight because their muscle tissues don't get enough glucose, the main energy source for the body's functions.