This is misleading; egg consumption was only cut because Britain's eggs (and bacon) were imported from Denmark. And people were encouraged to use meat drippings in place of butter, and use offals in place of meat, both of which were rationed, so it is unlikely fat intake as % of energy fell much (that the well-off were forced to reduce their total calorie intake across the board accounts for the lavish descriptions of meals in the books Evelyn Waugh wrote during the war, Put Out More Flags and Brideshead Revisisted).
An important contribution to the health benefits of rationing was, that the amount of wheat available for consumption by humans decreased, and people were encouraged to eat potatoes instead. More wheat (which was imported from the US and Canada) was fed to cattle for milk production (which was increased), and wheat for bread was milled at a lower extraction rate (less refined) to include more vitamins - a controversial policy as this also decreased its digestibility - and, supplemental B vitamins and calcium were also added to flour, for the first time in the UK. The story is summarised well in a chapter of the book Britain's War Machine.
Jack Drummond was famously murdered with his family in France after the war (a crime which has generated its own conspiracy theory industry among the French), and Magnus Pyke took his place as the don of Nutrition. Success in Nutrition is a 'studybook' (all the information needed to pass all the nutrition examinations of the day) he wrote in 1975, and is as excellent a nutrition text as anyone could wish for. There is a little nod to the lipid hypothesis, but it hasn't skewed the business of getting people properly fed yet - it's a work worthy of Drummond (to whom it is dedicated).
Magnus Pyke O.B.E., Ph.D., C.Chem, F.R.S.C., F.I.Biol., F.I.F.S.T., F.R.S.E. also, incredibly, according to Wiki, wrote the book 'Tricky and Portishead and Other Stonehead Bristol Sounds of the Future'. He makes an appearance (shouting "Science!") in this pop video, so that might even be true.
Anyway, I wanted to quote some words of wisdom from Success in Nutrition, from the chapter on Energy Intake: After warning that BMI does not give an accurate indication of health for everyone, and that variations in BMR render it extremely difficult to specify the right caloric intake for any individual, Professor Pyke concludes;
The most direct way of finding out whether an individual's energy intake is nutritionally adequate is to ask him whether he has enough to eat. If he says 'yes' and if his body weight is satisfactory, his energy intake is satisfactory too.
After discussing (i) different types of bodies, the next section covers
(ii) The influence of social ideas on the ideal body weight.
The purpose of good nutrition is health and health, let us repeat, can be defined as 'complete, physical, mental and social well-being and not merely the absence of ill-health and infirmity'. Different communities have different ideas about what they consider to be the appropriate body weight desirable for complete social well-being.
Although, as we shall explain later, there are certain technical methods for measuring obesity, which is a sign of malnutrition, there is a margin within which people can choose what kind of people they would like to be. A community which thinks a great deal (perhaps in fact too much) about health and nutrition and how its members look, who like their children to be big and their young men and women plump and buxom, may accept certain body weights as standards of optimum nutrition. In another community with a different idea of 'complete social well-being', where people consider that children should work, young men and women overcome strict tests before being accepted as full members of society, and adults think little of their appearance and more of some duty or purpose, considerably lower body weight may be accepted as normal. Yet, though it is difficult for a nutritionist to judge, both may be equally healthy although the members of one community may obtain more units of energy in their diet than those of the other.
- "it is difficult for a nutritionist to judge". Not words we've been hearing much in recent decades, which might be an example of the Dunning-Kruger effect in action.And very interesting that the ideal of a plump, buxom society should be the example chosen as recently as 1975. No-one, however eccentric, would choose that example today. Few nutritionists seem to be aware of the possibility of the existence of a healthy, plump, buxom society; they are more likely to be propagandists for "some duty or purpose", whether it be slimness, the hope of longevity, increased muscular development, or self-sacrificial attempts at saving the planet. In other words, a society's valuing "some duty or purpose" now includes it thinking "a great deal (perhaps in fact too much) about health and nutrition and how its members look".
A good addition to any library of classic nutrition texts, and one that makes me curious to read Pyke's other works, such as Synthetic Food, listed on the Wikipedia page. That book about Tricky and Portishead and the Stonehead Sounds of Bristol doesn't seem to be on Google, unfortunately.