Fat cells produce the protein sLR11 which inhibits fat burning.  The more fat a person has, the more protein sLR11 will be produced and the less calories burned, preventing weight loss.

 Fat storing hormones are insulin, Neuropeptide Y (NPY) which increases the number of fat cells in the body, and because estrogen is also produced by fat cells, it turns into a fat storing hormone. When your body is actively storing fat, it does not know how to lose weight.

  There are three ways to accumulate excess estrogen in the body; too much estrogen produced by the ovaries, adrenals and fat cells, acquired from the environment or diet or the body is unable to eliminate used up estrogen.

Chronic repeated exercising and/or extreme intensity coupled with extreme duration create chronic stress. If you are an untrained athlete, activities like long duration running or biking and high intensity calisthenics are chronic stress makers that actually hinder weight loss.