Initiation and perpetuation of obesity and obesity resistance in rats.
A search was made for predisposing factors and sequelae of diet-induced obesity (DIO) or resistance to DIO (DR). During 3 mo on a high-energy (CM) diet, two-thirds of the male Sprague-Dawley rats ate 16% more calories over the first 30 days and developed DIO. The remaining one-third were DR, gaining the same amount of weight as chow-fed controls. Basal and norepinephrine (NE)-stimulated in vivo O2 consumption, performed before rats were placed on the CM diet, was the same in those rats that later became DR or DIO after 3 mo on the CM diet. DR rats were 4% lighter, whereas DIO rats were equal to chow-fed rats before their exposure to the CM diet. When CM-fed rats were switched to chow, DIO rats took 14 wk to reduce their body and retroperitoneal fat pad weights to those of chow-fed controls, whereas DR rats gained only 40% of the body weight, and fat pads were 34% lighter than controls. After 14 wk, DIO rats were neither hyperinsulinemic nor insulin resistant, whereas DR rats had 64% reduced areas under their insulin curves after intravenous glucose (1 g/kg) compared with controls. Unlike younger rats, animals here had inconsistent plasma NE responses to intravenous glucose. Therefore the CM diet produces DR and DIO states that tend to become self-perpetuating once established.
Levin
B E
BE
Neurology Service, Veterans Administration Medical Center, East Orange 07019.
Hogan
S
S
Sullivan
A C
AC
D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D001835:Body Weight; D004032:Diet; D002149:Energy Intake; D007328:Insulin / Q000097:blood; D008297:Male; D009638:Norepinephrine / Q000097:blood; D009765:Obesity / Q000209:etiology / Q000503:physiopathology*; D010101:Oxygen Consumption; D051381:Rats; D011919:Rats, Inbred Strains; D015430:Weight Gain
D001786:Blood Glucose; D007328:Insulin; D009638:Norepinephrine