Antibody is a protein that reacts against an antigen in an animal-type organism. Antibodies, which can be found in the blood or other body fluids, are used by the immune system to recognize and block viruses, bacteria, parasites or fungi. The most frequent antibody is formed by structural basic units that have four chains: two light and two heavy. The B lymphocyte is responsible for synthesizing the antibodies, which can be divided into five different classes in the case of mammals.
it may be a medical problem but you yourself said you have poor eating habits and the can 100% cause weight gain. A burger fry and a drink is about your supposed daily intake. Eat right see if it help's otherwise go into a family/general/internist doc and get some test done.