You can not gain more calories than you consume. The weight of the food those calories can vary some but nobody will gain more weight than the same amount of food or even close to it
She was correct, the best feed to weight ratio for mammals is pigs. This number changes with the age of the pigs with the lowest being around 3.4 pounds of feed for each pound of weight gain. Some breeds of chickens go as low as 1.8 to 1.
You can not gain more calories than you consume. The weight of the food those calories can vary some but nobody will gain more weight than the same amount of food or even close to it