Hi, My Father Is At 62 Years Age. He Is

Question : Hi,
My father is at 62 Years age.
He is NOT having any significant medical ailment (like BP, Blood Sugar, Cholesterol etc) as per lab reports, other than following conditions:
1. Inguinal Hernia (about 20 Years) and unoperated, uses compressive belt
2. Glaucoma
3. Difficulty in digestion when taking some hard to digest food in moderate quantity. Therefore, takes only less than normal quantities of such food, to avoid digestion difficulty (which otherwise triggers loose motions)
4. Difficulty managing stress and almost always remain highly stressed/ worried on even small matters

The problem for which we need advise is that he is loosing weight since last few years and has lost about 6-8 kg weight in past 1-2 years without any visible reasons. Critically important point to note is that his food intake (total of whole day) is higher than other family members and has never declined. Since early morning about 7 to 8 am diet starts and continues on every 2-3 hours either in form of routine food items, biscuits, milk, fruits, snacks, horlicks etc and closes at about 9 pm evening. There is no restriction in food like oil, sugar etc - these are all included as per normal diet of normal person.
On advise from one doctor, he also took Ensure supplement for 5-6 months, but this also did not change the scenario.

Currently his weight has reduced to 50 kg (decline of 3 kg in past 6 months despite impressive food plan) and height is 166 cm.
He feels cold much higher than others. BP normally remain in range of about 110/75.

Some time back, there had been extensive tests and consultation like cardio, endochrine, gastro, GP etc. to figure out the root cause, however nothing could have been identified in lab tests.

Therefore, we need advise , as in which direction we should start to pin point the root cause for addressing it.

**hard to digest food - like dry fruits/ nuts (walnut, almond, cashew etc), non veg items etc.