Ghrelin and exercise have been known to stimulate the release of growth hormone which is related to the glucose metabolism. However, the age effects of exercise on ghrelin in energy consumption remain unclear. Young (3 month old) and middle-aged (12 month old) Sprague-Dawley male rats were overnight fasted, and then randomly partitioned into exercise and control groups. Exercise groups swam for 20 min in 25°C water. Rats immersed in 25°C water for 20 min were used as control animals. All blood samples were collected before and 10, 20, 30, and 60 min after initiation of exercise via the right jugular vein. Our results indicated that the swimming regimen decreased the secretion of acylated ghrelin and insulin, but increased the secretion of leptin, lactate, and glucose. In addition, exercise significantly amplified the inverse correlation between leptin and acylated ghrelin (r < -0.6) in middle-age group. Both the above findings were not emphasized in related articles before. Moreover, the time courses of these changes were slightly different in young and middle-aged rats. In basal metabolic characteristics, body weight and the plasma lactate, glucose, insulin, and leptin are higher in middle-age group than that in young group. In conclusion, compared with young rats, middle-aged rats have higher basal body weight, plasma glucose, insulin, and leptin, but age had no effect on the level of plasma acylated ghrelin. A 20-min exercise regimen decreased acylated ghrelin and increased leptin with inverse correlation between them which was strengthened during exercise, but were not influenced by age.