The transition in eating behaviour toward a diet rich in calories and low in vegetables is a major factor responsible for the rapid increase in the incidence of obesity and diabetes. The research aimed at investigating the effect of a high-calorie diet and vegetables on feeding behaviour, weight gain and blood sugar in male Wistar rats. The vegetables were dried, blended, and preserved in airtight containers. Thirty male Wistar rats weighing an average of 127.4 g were housed in 6 cages with 5 rats in each cage. There were six groups comprising the positive control which was fed standard rat feed and water, also the negative control which was given a high-calorie diet (high-fat feed and sugar water) and four treatment groups. The four treatment groups were fed on a high-calorie diet with a 5 % concentration of either Corchorus olitorius, Crassocephalum crepidiodes, Amaranthus hybridus or Solanecio biafrae respectively. Water (or sugar water) and feed intake of each group were measured and recorded daily. Weekly consumption of water and feed was computed for the entire 5 weeks of the experiment. The fasting blood sugar and weight of the test rats were recorded at baseline and weekly. Oral glucose tolerance test and serum insulin were determined at the end of the experiment using blood samples from the test rats. All results were analysed using ANOVA at p≤0.05 and means were separated with the use of Duncan’s multiple range tests (SPSS 20.0). The high-fat feed was significantly different from the standard rat feed in the composition of fat (26.79 g) and calories (422.67 kcal). The negative control and the treatment groups got adapted to feeding on the high-calorie diet before the end of the experimental period. Water and feed intakes of the positive control were only significantly higher during the first three and four weeks, respectively. At the end of the experiment, the positive control had the highest weight gain of 22 g which was significantly different at p≤0.05. C. crepidioides and S. biafrae significantly lowered the blood sugar (62.75 and 62.50 mg/dL) of the test rats. A. hybridus prevented insulin resistance by the attainment of peak level at 30 min alongside the positive control. There was a significant increase in the insulin level of the negative control while the vegetables prevented increased production of insulin. Key words: Blood sugar, Diabetes, Feeding behaviour, High-calorie, Insulin, Obesity, Vegetable, Weight gain