I am constantly amazed at the ignorance of medical authorities of the psychology as well as basic facts of nutrition. If someone has lost interest in food, all the things that diet sheets suggested you eat are just the things to kill your appetite.
If someone is not eating enough and is losing weight they need to be tempted to eat. Be offered small portions of food nicely presented.
What you need to do is look at the foods you normally eat and see how they can have their calory count increased. For example, if you are having boiled potatoes with a meal, make sure you put plenty of butter on them. If you have a salad, have mayonnais not salad cream.
Make sure that you do not make portions too big, I know that sounds odd, but a huge plate of food can be intimidating. A small plate of food, presented so that it is pleasing to the eye, on a pretty plate on a laid table, even just a kitchen table, is much more inviting to eat than a huge plate of pie and chips with gravy, so more likely to be eaten.
Have set times for meals, and stick to them. Then when you have your morning/afternoon/evening drinks always accompany them with several squares of milk or fruit and nut chocolate.
You clearly understand the rules of nutrition better than the person who gave you this ridiculous diet sheet. Chuck it away and bring your pwn natural intelligence to the issue.
Small quantities of food you really enjoy/enjoyed, attractively presented at regular meal times and enriched with butter, cheese, fruit and veg - and plenty f chocolate with your cups of tea and coffee.