As always, I think you can turn to Neil Tennant for advice.
In this case, not
"We're S-H-O-P-P-I-N-G
We're shopping"
but his 1980 work "The Dairy Book of Home Management" General Editor: Neil Tennant.
"Slimmers: A balanced diet is still necessary but as we normally eat many foods to excess, we can safely cut down without damaging our health. Try not to rule out foods with a high nutritional value, such as milk, cheese, meat, fish, eggs, fruit and vegetables, although the amount you eat of each may need to be reduced. Cut down on sugary foods such as cakes, sweets and biscuits, which contribute very little to the diet. Fatty foods and fried foods are also high in calories, as is alcohol, and consumption of these should be watched and strictly limited".
Bonus tip:
"Invalids: Colourful edible garnishes can play a significant part in invalid cookery".
Interestingly also:
"Diabetics: The treatment of all diabetics, even those who require insulin, will necessitate some degree of dietary restriction. The diabetic's intake of carbohydrate foods must be controlled. Once the basic principles of the carbohydrate exchange system are understood, the diabetic's meals can easily fit in with those prepared for the rest of the family."
(This book is obviously sponsored by the dairy industry, but on the plus side there is a recipe for basic cream mould and baked egg custard if anybody is interested).