Digestive problems with weight loss and.

My father has a long-term habit of eating only one meal a day and has had poor digestion since a young age. Recently, his appetite has declined further, and he finds it difficult to digest many foods. He avoids paneer, milk, ginger, oily, and outside food due to acidity and indigestion, and now also due to fear of discomfort. His routine has also been irregular during his working life. Last year, during house construction (June–October), he experienced physical strain followed by loss of appetite, poor sleep, and weight loss. Although he feels he is slowly recovering, I still notice ongoing weight loss and intolerance to foods like eggs and halwa, which he previously tolerated. He takes no medication. Blood tests are normal except for slightly low haemoglobin. He feels weak and gets tired easily but has no dizziness. I am concerned about his nutrition and overall health, and would like guidance on whether to consult a specialist or improve his diet plan.