A very important and interesting feature of some lectins is their ability to mimic hormones. As one can imagine, this could contribute to a significant impact on metabolism. The hormone insulin stores excess carbohydrates (glucose) as fat. It accomplishes this by attaching itself to the insulin receptor found on the fat cell. Under stimulation from insulin, the fat cell becomes more permeable to glucose, which would otherwise remain in circulation. With mission accomplished, the insulin hormone then disconnects to its receptor.

In many people, lectins found in lentils, green peas, corn, potatoes but especially wheat germ agglutinin (WGA), are known to bind to the insulin receptor giving the fat cell the same message that insulin gives, namely to make fat. The lectin, however, due to a lack of feedback inhibition, remains indefinitely attached to the receptor giving the cell a constant message to make fat. This perhaps explains why many weight loss programs that include a moderate-to-high amount of carbohydrate (especially modern grain) fail.

One other point with regard to lectin contribution in weight gain is the fact that lectins have been shown to block digestive hormones. WGA can bind to the receptor for cholecystokinin (CCK), a hormone involved in appetite control, suppressing its function. This essentially leads to an increase in appetite and impairment in the release of digestive enzymes.