Rheumatoid arthritis
It is an autoimmune disease that makes your immune system attack the lining of your joints, eventually leading to inflammation. Chronic inflammation can speed up the metabolism and reduce your weight. Symptoms of rheumatoid arthritis include joint swelling and pain. It usually affects the same joints on both sides of your body.
Diabetes
Unexplained weight loss can occur due to type 1 diabetes. If you have it, your immune system attacks cells in your pancreas that make insulin and without insulin your body can’t use glucose for proper energy. This causes high blood glucose. Your kidneys remove unused glucose through urine. As sugar leaves your body, so do calories.