Several studies concluded that diets low in fat (under 15% of total calories) significantly decreased testosterone levels while diets higher in fat (above 30% of total calories) increased serum testosterone levels. Rather than continuing with this discussion I will provide a link to an article which covers the subject quite nicely. To simplify everything that I have said, it seems that one should not lower fat below 15% of daily calories unless they would like to face extreme testosterone deficiencies. Likewise, one should not increase fat to say 40% in order to increase testosterone. Although fat increases testosterone to a degree, it is important to remember that testosterone is only a small piece of the larger puzzle. There are many other hormones and factors involved in building muscle other than just testosterone. By increasing fat to extremely high levels, there will be less “space” for carbohydrates and protein, both of which are very important for aforementioned reasons.
Side effects are minimized by taking the lowest doses possible (that still yields positive results) and following doctor's orders. It is important to avoid self-regulation of the dosage, either by adding more or stopping the drug without a schedule. After prolonged use, steroids must be gradually reduced to permit the adrenal glands to resume natural cortisol production. Eliminating doses too quickly can result in glucocorticoid withdrawal symptoms, worsening of underlying inflammatory disease (rebound effect), or rarely, adrenal crisis (a life-threatening state caused by insufficient levels of adrenal steroids).