In these twiddly days of the Christmas perineum, your mind naturally drifts to corpulence, both your own and that of those around you. I have before me The Home Doctor, a 391 page layman’s version of Black’s Medical Dictionary published in 1931. Under the heading of “corpulence” — a word it uses interchangeably with “obesity” — it identifies the causes as being a “luxurious, inactive, or sedentary life, with over-indulgence in sleep and absence of mental occupation”, but above all “over-feeding” especially with “fatty, sugary, and starchy elements”. 

The Home Doctor notes that “women are prone to become more corpulent than men”, a claim that is borne out by modern obesity statistics, although the difference between men and women is quite small. It also notes that “health cannot be long maintained under excessive obesity”, although “even a considerable measure of corpulence, however inconvenient, is not incompatible with a high degree of health and activity, and it is only when in great excess or rapidly increasing that it can be regarded as a morbid state.”

While obesity is far more common today than it was in the 1930s, the belief that it was virtually non-existent until fifty years ago has no evidence to support it. We have little idea of how many people were obese in the 1970s, let alone the 1930s. The Body Mass Index (BMI) was devised in the 19th century, but there were no systematic attempts to measure obesity at the national level until the late 20th century. 

The Home Doctor does not refer to Body Mass Index. Instead it provides a table showing the average weight measurements of thirty year old men of various heights and suggests that anyone whose weight exceeds the average by more than 1/7th may be considered corpulent. Translating these thresholds into BMI, we get the following cut off points:

5 ft 8” : 12 st 9  =  26.9 BMI

5 ft 9”: 13 st 3 =  27.3 BMI

5 ft 10”: 13 st 11 = 27.6 BMI

5 ft 11”: 14 st 3 = 27.7 BMI

6 ft: 14 st 7 = 27.5 BMI

For a rough and ready calculation, The Home Doctor produced quite a consistent definition of corpulence of around 27.5 BMI. The modern threshold for overweight is a BMI of 25 while the threshold for obesity is a BMI of 30. The Home Doctor’s rule of thumb gives us a threshold of corpulence that is mid-way between overweight and obese today. 

But The Home Doctor had a special clause for people as they get older, saying: “An addition of about three pounds for every four years of age over thirty must be made to the above figures, as the weight tends naturally to increase until old age sets in.” So, for example, the average weight of a man aged 46 who is 5 feet and 11 inches tall would be expected to be 13 stone and 6 pounds (26.2 BMI) and he would be corpulent at 15 stone and 5 pounds (29.9 BMI). That is just a whisker away from the modern threshold for obesity.

If this book is any guide, doctors in the 1930s had a similar idea of what constituted obesity to doctors today. They more or less expected people in middle age to be overweight (by today’s definition) while setting the bar for obesity a little lower than we do now. 

Under the entry for “calorie”, The Home Doctor notes that people in “ordinary sedentary occupations” need 2,500 calories a day, whilst those engaged in “light muscular work” need 3,000 and those engaged in “hard continuous labour” need 4,000. This might surprise Chris van Tulleken, but it seems pretty obvious to everyone else. Today, men are advised to consume 2,500 calories and women 2,000. There is no advice for people who do strenuous work, perhaps because so few of us do it.

The book contains a few entries that catch the eye of the modern reader, either because they are amusingly archaic or politically incorrect. Some, perhaps, contain lost wisdom. The entry for “baldness” describes it as “a condition largely associated with the habits of civilisation, and said not to occur in those primitive peoples who live constantly an open-air life”. “Idiocy” is described as “a profound degree of mental defect in which the person is unable to guard himself against ordinary dangers and is of dirty habits”. “Imbecility” — which sounds worse — is actually better, being “a term applied to feeble-mindedness in which the mental powers are somewhat greater than those possessed by an idiot”.

Inevitably, it is the entry for “tobacco” that offers the greatest contrast with modern health advice. The Home Doctor explains that “a very small amount of nicotine, such as that derived from a single cigarette, has a decidedly stimulating effect upon the mental and bodily powers”. It adds that “the most suitable time for smoking is generally admitted to be after meals, and especially in the evening when the day’s work is at an end, when the sedative action is most beneficial to the nervous system.” 

But it is not all good news. “Among the evil effects of smoking,” it says, “may be mentioned the temporary nausea, depression, giddiness, and vomiting which affect the unaccustomed smoker. These effects, however, pass off quickly, and the tendency to their occurrence disappears as the person is habituated to tobacco.” It concludes that: “Generally speaking, excessive smoking is a hurtful thing, particularly for young people, and a liberal allowance of tobacco for a healthy, full-grown man is usually fixed at a maximum of four ounces [113 grams, i.e. a lot] in the week.”

Such complacency becomes more understandable when you look up the entry for lung diseases. While the subject of corpulence is given more than two pages in The Home Doctor, the obscure disease of lung cancer gets just sixteen words: “Tumors of the lung are not of frequent occurrence, though cancer occasionally begins in the lung.” Sadly, that would soon change.

Merry Christmas, and be careful not to smoke excessively in the new year.