Jean-Francois Dancel

Jean-Francois Dancel (a French physician) presented his thoughts on obesity in 1844 to the French Academy of Sciences and then published a book, Obesity, or Excessive Corpulence: The Various Causes and the Rational Means of a Cure.
“All food which is not flesh ―all food rich in carbon and hydrogen [i.e., carbohydrates] ―must have a tendency to produce fat,” wrote Dancel.

Dancel also noted that carnivorous animals are never fat, whereas herbivores, living exclusively on plants, often are. (*snip*)

Dancel claimed that he could cure obesity “without a single exception” if he could induce his patients to live “chiefly upon meat," and partake “only of a small quantity of other food."

Dancel argued that physicians of his era believed obesity to be incurable because the diets they prescribed to cure it were precisely those that happened to cause it. (pp.151-152)

https://www.en-futoraba.com/topics/2018/10/22108/

At the same time these authors universally forbid the use of meat, and permit only an exclusively vegetable diet. Any one, after reading the preceding pages, is competent to judge how great must be the error of these writers, who always end, however, by affirming obesity to be incurable. Incurable, no doubt, it is, by such treatment. But to diminish obesity, without affecting the general health, the patient must feed chiefly upon meat. I say chiefly, because man, being naturally dis[65]posed to partake of both animal and vegetable food, cannot live exclusively upon meat without prejudice to his general health. The use of a small quantity of vegetable matter will not prevent the diminution of fat. At a future page the several alimentary substances will be arranged from a chemical point of view, in the order they truly occupy as reducing or inducing obesity. For the present, it may be stated that among alimentary substances, exclusive of meat, those containing the greatest amount of water, such as watery vegetables, sweet fruits, &c., have an especial tendency to develop fat. The result of my own observation, in a great number of cases, is in perfect accordance with the chemical fact, viz., that the chief constituents of fat are also constituents of water. So that although a person should live exclusively upon meat, and at the same time drink a great deal, he would not experience any perceptible reduction of fat. This affords an explanation why many who eat very little, but drink large quantities of water, beer, cider, brandy or wine, labour under obesity. Whoever desires to avoid corpulence must therefore feed chiefly upon meat, partaking very sparingly of any other kind of food, and at the same time should drink but little.

If a supply of fat, equal in combining proportion with the alkali ingested, be supplied by means of food to the body, the action of the alkali upon the previously deposited fat constituting the obesity, must be null. For the speedy reduction of obesity, therefore, the food must contain a less than ordinary amount of the elements of fat, by making it to consist chiefly of meat, and bringing about a reduction of the superabundant fat by means of alkalis, which should be administered in every variety of form, in order not to induce a sense of disgust on the part of the patient.