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Background/aim: Obesity is a multifactorial disease and the treatments include dieting, exercises, drugs and various surgical procedures. Recently, we reported that gastric bypass surgery caused body weight loss without reducing food intake and that high-fat diet-induced obesity was associated with increased calories per meal but not per day in rats. In the present study, we examined the food intake, eating behavior and metabolic parameters in rats underwent bilateral truncal vagotomy, sleeve gastrectomy and duodenal switch procedures.Methods: Body weight (BW) was recorded weekly throughout the period of the study. The food intake, eating behavior and metabolic parameters were measured pre- and 2 or 9 weeks post-operatively by a comprehensive laboratory animal monitoring system (the so-called CLAMS). Adult rats were subjected to bilateral truncal vagotomy plus pyloroplasty to prevent gastroparesis (VTPP), pyloroplasty alone (PP) or sham operation as controls. 10 weeks after completing CLAMS measurements, sleeve gastrectomy (SG) or duodenal switch (DS)(without SG) was performed in sham- or PP-operated rats, respectively, and the same CLAMS measurements were repeated as before. Afterwards, the SG-rats were subjected to DS and the VTPP-rats were subjected to both SG and DS simultaneously. Results: Survival rates were 100% for sham- (7/7), PP- (7/7) and VTPP-operations (7/7), 86% for SG (6/7), 71-83% for DS alone (5/7) or DS with SG (5/6) that was performed early, and 14% for SG+DS (1/7) that were performed at the same time. VTPP reduced BW (10%) transiently (1 week post-operatively), while PP- or sham-operation was without the effect. SG caused a reduced BW (10%) for 6 weeks, while DS alone or SG followed by DS led to a continuous BW loss from 15% at 1 week to 50% at 9 weeks postoperatively. Food intake was higher and satiety ratio was lower during nighttime than daytime in all groups of surgeries. VTPP was without any measurable effects on food intake, eating behavior and metabolic parameters. SG increased drinking activity and energy expenditure but was without the effects on food intake and eating behavior. DS regardless of accompanying with SG reduced food intake by about 60% during nighttime but not daytime, and did not affect energy expenditure. Conclusions: Weight loss after VTPP, SG or DS differed in terms of degree, duration and underlying mechanisms. DS without SG was most effective in long-term, at least partly due to the reduced food intake. In addition to food intake and eating behavior, possible involvements of absorption, gut hormones and the brain-gut axis need to be further studied.