Practical observations suggest that there is a threshold level where no further fat-loss benefit is gained and potentially a reversal is experienced. It is quite easy to pick out the smooth physiques of men using more than 1,200mg/week of a testosterone ester, much of the smoothness being due to water retention and a poor attention to diet. However, in looking at the direct effect sex steroids (testosterone, DHT and estradiol) have on fat cells, one can see a potential reason for this.

The Deal With Fat
Fat cells were long believed to be simple storage sites for fat, neither contributing nor responding to the metabolic signals of the body other than an increased energy demand due to exercise or starvation. However, it has been learned that fat tissue is an endocrine organ, sending out hormones that affect body composition, appetite and metabolism. Fat also releases a number of proteins that increase inflammation, which can reduce insulin sensitivity and negatively affect cardiovascular health. Fat also responds to hormonal signals from other tissue, much like muscle, which grows when stimulated by testosterone or insulin.

Among the many hormones that stimulate fat cells are the endogenous (natural) steroid molecules, including androgens, estrogens and glucocorticoids (cortisol). In a manner that would be very surprising to many physicians trained prior to the 1990s, fat cells alter steroid concentrations by means of steroid-metabolizing enzymes. Cortisol, the active form of the catabolic steroid that is associated with muscle loss, actually promotes fat gain. Inside the fat cell, cortisol is generated from an inactive form called cortisone. A clear association between high levels of the enzyme that activates cortisol and obesity has been reported.