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Objective: To determine whether a supplement of soy protein improves body composition, body fat distribution, and glucose and insulin metabolism in postmenopausal women without diabetes compared with an isocaloric casein placebo.

Design: Randomized, double-blind, placebo-controlled 3-month trial.

Setting: Clinical Research Center.

Patient(s): Fifteen postmenopausal women.

Intervention(s): Computed tomographic scans at L4/L5, dual energy x-ray absorptiometry, hyperglycemic clamps.

Main Outcome Measures: Total fat, total abdominal fat, visceral fat, subcutaneous abdominal fat, and insulin secretion.

Result(s):

• Weight by dual energy x-ray absorptiometry did not change between groups (+1.38 +/- 2.02 kg for placebo vs. +0.756 +/- 1.32 kg for soy, mean +/- SD).
• Total and subcutaneous abdominal fat increased more in the placebo group than in the soy group (for differences between groups in total abdominal fat: +38.62 +/- 22.84 cm(2) for placebo vs. -11.86 +/- 31.48 cm(2) for soy; subcutaneous abdominal fat: +22.91 +/- 28.58 cm(2) for placebo vs. -14.73 +/- 22.26 cm(2) for soy).
• Insulin secretion, visceral fat, total body fat, and lean mass did not differ between groups.
• Isoflavone levels increased more in the soy group.

Conclusion(s): A daily supplement of soy protein prevents the increase in subcutaneous and total abdominal fat observed with an isocaloric casein placebo in postmenopausal women.

Source: Fertility and Sterility, Dec 2007; 88(6) 1609-17. PMID: 17412329, by Sites CK, Cooper BC, Toth MJ, Gastaldelli A, Arabshahi A, Barnes S. Departments of Obstetrics, Gynecology and Pharmacology, University of Alabama at Birmingham, Alabama; Departments of Obstetrics, Gynecology and Medicine, University of Vermont, USA; Institute of Clinical Physiology and Department of Medicine, University of Pisa, Italy. [E-mail: csites@uab.edu]