The rules of the low carb diet from the study are simple:
The instructions relating to the low carbohydrate diet were identical to those given to patients attending a hospital overweight clinic under our supervision. Essentially, the subjects were asked to take between 10 and 20 oz milk daily (about 300-600 ml), and as much meat, fish, eggs, cheese, butter, margarine, cream and leafy vegetables as they wished. The amount of carbohydrate in other food was listed in “units” with each unit consisting of 5 g carbohydrate; the subjects were told to limit these foods to not more than 10 units (or 50 g) carbohydrate daily.
Both studies provided between 1500 and 1600 kcal per day, but with huge differences in outcome. In the Key’s semi-starvation study (high-carb, low-fat) the subjects starved and obsessed on food constantly. In the Yudkin study (low-carb, high-fat), the subjects, who had no restriction on the amount of food they ate, volitionally consumed the same number of calories that the semi-starvation group did, yet reported that they had “an increases feeling of well-being.” Instead of lethargy and depression reported by the Keys subjects on their low-fat, high-carb 1570 calories, those on the same number of low-carb, high-fat calories experienced “decreased lassitude.”It is fascinating to think that people on a high-fat diet would voluntarily restrict their calories so much, and report feeling high energy.
We feed pigs grain (high carb). Depending on their age, we feed them either corn or wheat. Both of those diets help the pigs to get fat (and wheat makes harder, whiter fat than corn).
Pigs love corn. Besides meat, it is hard to find something they like more. I'm guessing that like humans, it tastes sweet, jerks their insulin around and makes them hungry -- for more corn. The big pigs eat 5 to 6 pounds of feed a day. That's like eating a 5# bag of corn meal or flour, day after day.
At the end of their lives, we put the pigs on a wheat-based diet.* That really slows their gains (from around a pound a day to around .8 pounds per day), and they get a bit leaner. It is like switching them from grits to cream of wheat - if you've tried both, you know that it is a lot easier to eat a massive amount of grits than cream of wheat. The wheat "sticks to the ribs" more than the corn.
Just a small change in diet - from one high carb diet to another - results in a much slower rate of weight gain. Of course, the pigs are still getting fatter and fatter; that's the whole point.
Old books (from the 1800s) confirm the superiority of corn for fattening pigs:
Having seen how pigs respond to corn, it doesn't surprise me that a low-carb diets help people to lose fat. Obviously high-carb (particularly corn-based) diets make it very easy for pigs to gain fat. Humans and pigs are very similar - we are both omnivores, roughly the same size, etc.
* When we switch the pigs from corn to wheat is important. Do it too early and it takes the pigs forever to finish, which costs a lot more and impacts pigflow (pigs won't be ready on schedule). You need to know the desired final weight before switching the pigs to wheat.