T Nation

Hi carb,low fat diet reduces free testosterone levels

Fellow T-men might be interested in the following abstract.In this study administering a hi carb,lo fat diet increased levels of SHBG,which consequently reduced levels of free testosterone.The authors actually think this is great as they believe it may lower the risk of prostate cancer,compared to consuming a higher fat diet.However the higher fat diet they refer to is the shitty SWD (standard western diet),which contains high levels of saturated and trans fatty acids(along with excessive salt and sugar).
My own blood work showed lower SHBG and higher free test levels upon switching to a low carb,higher fat diet.
Here 'tis:

Effects of Diet and Exercise on Insulin, Sex Hormone-Binding Globulin, and Prostate-Specific Antigen
Christopher N. Tymchuk, Sheva B. Tessler, William J. Aronson, and R. James Barnard

Abstract
A diet high in fat has been linked to prostate cancer, possibly through an influence on hormones. Sex hormone-binding globulin (SHBG) binds androgens and is regulated in part by insulin. Diet and exercise can modify insulin levels, potentially affecting SHBG and the biologically available levels of androgens. To determine the effects of a low-fat (<10% of calories), high-fiber diet plus daily exercise on insulin, SHBG, prostate-specific antigen (PSA), and serum lipids, we measured the levels of these factors in the serum of 27 obese men undergoing a three-week diet-and-exercise program. Insulin decreased from 222 ± 30 to 126 ± 21 pmol/l (p < 0.01), and SHBG increased from 18 ± 2 to25± 3 nmol/l (p < 0.01). Body mass index decreased from 35 ± 1.9 to 33.4 ± 1.8 kg/m 2 (p < 0.01). PSA levels were normal and did not change significantly, although in a small subset of men (n = 3) with slightly elevated PSA levels (>2.5 ng/ml) all showed a decrease. The three-week diet-and-exercise intervention decreased insulin and lipid levels while increasing SHBG. The increase in SHBG would result in more testosterone being bound and, therefore, less of the androgen available to act on the prostate. The decrease in insulin might also decrease mitogenic activity in the prostate. The diet-and-exercise regimen did not have a significant impact on normal PSA levels. Although modest, these changes may be protective against the development of prostate cancer.
[Nutrition and Cancer 31(2):127-131, 1998. © 1998 Lawrence Erlbaum Associates, Inc.]

A brief comment, you didn’t notice that esrogen drops 50% on the diet as well (Am J Med 1985 Jan;78(1):23-7); estrogen and/or T/DHT may also play a role. Still unk. One thing we do know is that IGF-1 drops on this diet and this induces prostate cell apoptosis, necrosis, decreases growth, etc. This data is unpublished.
Most high-fiber, low-fat diet studies show total T relatively unchanged or drop slightly, free T drop, E drop, Ins drop, IGF-1 drop and binding proteins increase. (IGFBP-1, SHBG, etc).

“Body mass index decreased from 35 ± 1.9 to 33.4 ± 1.8 kg/m 2” … 33.4 ± 1.8 could still put them over 35… meaning nothing much happened there.

BMI wouldn’t change much in 21 days, so no surprise there.