Some studies suggest that increased consumption of
soy protein hydrolysates may cause
body weight loss but the mechanism of action is unknown. The objective of this investigation was to determine whether intracerebroventricular (i.c.v.) infusion of
soy protein hydrolysates decrease food intake and
body weight. Adult male Sprague Dawley rats (n = 24) received i.c.v.
injections of soy hydrolysate I (SH I) or soy hydrolysate II (SH II) three times weekly for 2 weeks.
Krebs solution and
leptin were used as negative and positive controls respectively. SH I (6.5-20 kDa with a strong band at 14 kDa) was produced by hydrolysis with
alcalase, and SH II (approximately 2 kDa) was obtained by hydrolysis and ultrafiltration.
Leptin successfully reduced
body weight (-1.60 g) 24 h (p = 0.0093) after the third injection. SH I caused significant (p = 0.0009) decreases in
body weight (-1.70 g) 24 h after the third injection but not after 48 h. SH II showed a tendency to prevent
body weight gain but this effect was short of statistical significance (p < 0.40). Food intake was not affected by any of the soy hydrolysate treatments but
leptin injection did cause significant decreases in food intake (p < 0.05). Data suggest that soy
alcalase hydrolysate can decrease, in the short term, the rate of
body weight gain independently of food consumption. This preliminary data show that soy
peptides may play a role on
body weight regulation, possibly by increasing energy utilization.