Calories and gastric emptying: a regulatory capacity with implications for feeding.

Gastric emptying in four unanesthetized male Macaca mulatta was studied with the serial test meal method of Hunt and Spurrell. Liquid meals were infused into the stomach through a chronic indwelling Silastic cannula. Saline meals empty rapidly and exponentially. Doubling the volume of saline from 150 to 300 ml increased the emptying rate so that the half-life remained unchanged (15 min). The 150-ml glucose meals (0.05, 0.125, and 0.25 g/ml) emptied more slowly than saline, progressively more slowly with increasing concentrations (0.05--1.8, 0.125--0.78, and 0.25--0.37 ml/min) and linearly through most of their course. Doubling the volume of 0.125 g/ml-glucose meal did not change the rate of emptying. Converting grams of glucose to their caloric content, the emptying rate in kcal/min becomes constant (approx 0.4 kcal/min) in this range of concentrations. Isocaloric casein hydrolysate and medium-chain triglyceride oil meals at 0.5 kcal/ml empty at the same rate as glucose. The precision of this regulation is sufficient to give it a role in preabsorptive satiety and the control of caloric intake.