unwanted weight loss

Thank you for your question.
Many disease may cause weight loss.
Cancer is the most common, however, various autoimmune illnesses may also cause weight loss. ALS, amyotrophic lateral sclerosis, might also cause weight loss.
A change in your diet might result in weight loss.
The most important thing to do is consult your physician who can run blood tests and also CT and

also MRI scans which might reveal the cause of your weight loss.
Please keep a diary so that you can show it to your physician.
Sincerely,
Dr. Madhup Joshi