Hypothalamic hyperphagia and obesity in rats with jejunoileal bypass.

Jejunoileal bypass or sham surgery was performed in adult female rats followed 35 days later by ventromedial hypothalamic (VMH) knife cut or sham surgery (forming groups Bypass-VMH, Bypass-Sham, Sham-VMH, and Sham-Sham). Bypassed rats receiving VMH cuts (Bypass-VMH group) ate more food and gained more weight than did either Bypass-Sham or Sham-Sham groups. The hyperphagia and obesity of the Bypass-VMH rats was, however, substantially less than that of the sham bypass VMH cut rats (Sham-VMH group). Bypass-VMH rats that had their intestinal tract reconnected increased their food intake and ultimately became as obese as the Sham-VMH rats. Two additional groups received VMH knife cut or sham surgery followed 50 days later by jejunoileal bypass surgery (VMH-Bypass and Sham-Bypass groups). At the time of the bypass the VMH-Bypass group was hyperphagic and obese, but after surgery they underate and lost weight until they eventually stabilized their body weight at a level below that of the Sham-Bypass group. The body weight of the VMH-Bypass group was also 167 g less than that of the Bypass-VMH group. Thus, the order of surgery significantly influences the food intake and body weight level of rats with VMH knife cuts and jejunoileal bypass.