Counterregulation of insulin by leptin as key component of autonomic regulation of body weight

Figure 4 The effects of variable meal size (A) and energy variability (B) on the plasma concentrations of insulin (A and B), GIP (C and D) and leptin (E and F) under the conditions described in Figure 2. Insulin showed significant postprandial increases to meal size (A) and TPN (B) (F_df4,45 = 25.7; P < 0.0001), whereas GIP responded only to meal size (F_df4,45 = 42.3; P < 0.0001). Neither insulin nor GIP responded to exercise energy expenditure. Plasma leptin concentration slowly and progressively decreased in response to reduced energy availability caused by small meal (F_df4,36 = 48.1; P < 0.0001) and exercise (F_df4,36 = 39.1; P < 0.0001), and this response was abolished by large meal and TPN. Data from Ref. [39].