Reduction In Voluntary Food Intake Research Articles

Effects of subdiaphragmatic vagotomy on energy balance and thermogenesis in the rat.

Subdiaphragmatic vagotomy caused chronic gastric distension and hypertrophy, and a reduction in voluntary food intake in rats fed a pelleted stock diet. These effects were minimized by feeding a more digestible semisynthetic diet. Vagotomized rats fed the pelleted diet showed lower rates of oxygen consumption than pair-fed controls, and the rise in metabolic rate (thermic response) following gastric intubation with a carbohydrate meal was diminished. This could be restored to normal by simultaneous injection of insulin. Thermic responses to fat and noradrenaline were normal in the vagotomized group. On the powdered semisynthetic diet, vagotomized rats gained more weight and showed greater efficiency of energy gain than pair-fed controls. The thermic response to a single meal of the semisynthetic diet was depressed in these vagotomized rats, but restored to normal by acute insulin treatment. The activity of the thermogenic proton conductance pathway in brown adipose tissue mitochondria (assessed from purine nucleotide binding) was reduced by vagotomy in animals on both diets, but was restored to normal by chronic insulin treatment, which also slightly raised brown fat activity in sham-operated rats. These results demonstrate that the reduced gastric activity and food intake following vagotomy is dependent on the digestibility and/or composition of the diet. When differences in food intake are abolished by pair feeding, vagotomy reduces thermogenic responses to carbohydrate, probably as a result of impaired insulin release. This may be responsible for the enhanced energetic efficiency and elevated weight and energy gains seen after vagotomy.

Metabolic alterations induced by chronic heat exposure in the rat: the involvement of thyroid function.

The effects of chronic exposure to high environmental temperature (34 degrees C) on T4 production rate, food-intake, growth-rate and resting metabolic rate were investigated in adult male rats. This study was designed to examine the extent of variations and possible relationships between these parameters. As compared to control rats of the same body weight kept at 25 degrees C, rats exposed to 34 degrees C for 3-4 weeks exhibited a retarded growth-rate: 2.3 vs 4.0 g/day, a reduced food-intake: 15.2 vs 23.2 g/day, a decreased T4 production-rate: 1.8 vs 2.7 micrograms/day and a decreased oxygen consumption: 4.0 vs 5.4 ml/min. Heat-exposure altered the 4 parameters to a similar extent. T4 supplementation (3 micrograms/day) which induced a decrease in plasma TSH concentration, did not restore a normal growth-rate in heat-exposed rats. The decreased food-intake of the heat-exposed rats was not associated with any significant changes in the daily pattern of variations of liver glycogen content, or in the mean daily levels of blood glucose or insulin. The ratio T3 to rT3 in plasma was not altered by chronic heat exposure. When rats which had been chronically exposed to heat (25 days at 34 degrees C) were exposed to 25 degrees C, growth-rate, food-intake and oxygen consumption rapidly increased to control values whereas the rate of T4 production remained low. It is concluded that (1) a decrease in thyroid hormone economy is not directly involved in the alterations of growth and energy expenditure in rats chronically exposed to heat, (2) heat exposure does not lead to the establishment of a fasted state resulting from a large reduction in voluntary food intake, (3) metabolic alterations induced by heat exposure are rapidly and completely reversible upon decreasing the environmental temperature.

Voluntary food restriction by laying hens mediated through dietary self‐selection

1. Individually caged Single Comb White Leghorn hens simultaneously received two diets which allowed selection of certain nutrients: these “ split‐diets “, essentially provided concentrated sources of either protein and energy (191 g crude protein, 12.82 MJ ME and 4.7 g Ca/kg diet), or calcium (107 g CP, 7.28 MJ ME and 131 g Ca/kg). 2. During four, 28‐d periods of lay, birds offered these split‐diets consumed some 7% less food in total than did control birds receiving a conventional diet ad libitum. 3. Calculation of nutrient intakes showed that birds on the split‐diets consumed significantly less protein, energy and calcium than the control birds. 4. Giving split‐diets also resulted in superior shell quality; treatment differences were also noted in the timing of oviposition. 5. It is suggested that the voluntary reduction in food intake noted for birds offered split‐diets is associated with an appetite for calcium.

Behavioral compensatory responses to continuous duodenal and upper ileal glucose infusion in rats

A 30% glucose solution contributing 38% of the rats' normal voluntary daily energy intake was infused continuously for 24 hr into the intestines of two groups of rats, one catheterized in the duodenum and one in the upper ileum. Both groups responded by a compensatory reduction in voluntary food intake which was achieved by a statistically significant reduction in meal size but not in meal number. No significant change in food intake behavior occurred during similar infusion of equiosmotic NaCl solution, physiological saline or water. No significant differences in food intake behavior were observed between the group infused duodenally and the one infused intraileally. These findings suggest that, first, if an intestinal satiety mechanism exists, it is not exclusively located in the duodenum and, second, that any specific duodenal factors such as cholecystokinin are not indispensable in the control of meal-taking behavior.

Control of food intake during continuous injection of glucose into the upper duodenum and the upper ileum of rats

Duodenal factors have been implicated to participate in the elicitation of satiety during a single meal. This report evaluates the possible involvement of the upper small intestines in the day-to-day control of food intake. Glucose solutions, contributing about a third of the daily caloric intake of rats, were continuously injected into the gastrointestinal tract through a permanent catheter. The catheter was inserted into each animal at one of two locations: the upper duodenum and the upper ileum. There were five animals in each catheter group. Voluntary food intake was measured before and during glucose injection. Control injections of oil equicaloric to glucose and NaCl equiosmotic to glucose were also performed. All glucose injections resulted in a reduction in voluntary food intake which began as early as the first day of injection and compensated for most of the caloric content of the injected glucose. The reduction was similar for the two catheter groups. Equicaloric injections of oil produced an effect similar to glucose, while equiosmotic NaCl injections did not. It is concluded that if there is an intestinal metering system which participates in day-to-day control of food intake, it is not exclusively located in the upper small intestines.