Effects of short term nutritional manipulation on organ size and fasting heat production

Two studies were conducted to study the effects of short term nutritional manipulation on the organ size and the fasting heat production of pigs and sheep. The results of these studies indicate that fasting heat production can differ up to 40 per cent for animals of same age and weight, but with different nutritional backgrounds. Those animals on a higher plane of nutrition preceding measurements had higher fasting heat production, in spite of being the same age and body weight. At the same time, the weights of metabolically active organs such as the stomach, the small and large intestine, the liver and the kidneys are also very sensitive to the nutritional manipulation, in a parallel direction to that observed with fasting heat production. These findings provide strong evidence that the energy expenditures of the metabolically active tissues account for a significant amount of basal metabolic activity far in excess of the proportional weights of these tissues.