Weight loss and lipid changes with low-energy diets: comparator study of milk-based versus soy-based liquid meal replacement interventions.

OBJECTIVES

Soy protein intake has favorable effects on body weight and fat distribution in experimental animals but these effects have not been demonstrated in humans. To compare effects of soy- vs. milk-based meal replacements (MR) we assessed weight loss and serum lipoproteins changes for obese subjects who consumed low-energy diets (LED) including either milk-based or soy-based MR.

METHODS

Overweight or obese women and men (body mass indices 27-40 kg/m(2)) were randomly assigned to LED providing 1200 kcal/day, with consumption of five soy-based or two milk-based liquid MR for a 12-week weight loss trial. Serum lipoprotein measurements were obtained at baseline, 6 and 12 weeks.

RESULTS

For soy and milk MR groups, subject numbers were, respectively, 51 and 39 randomized and 30 and 22 completers. MR use averaged: soy, 3.7/day; and milk, 1.9/day. Weight losses for completers at 12 weeks were: soy MR, 9.0% of initial body weight (95% confidence intervals, 7.3-10.6%); and milk MR, 7.9% (5.8-8.8%) with no significant differences. Reductions from baseline in serum cholesterol and LDL-cholesterol values, respectively, at six weeks were significantly greater (P < 0.015) with soy MR (15.2% and 17.4%) than with milk MR (7.9% and 7.7%). Soy MR use was associated with significant reductions in serum triglycerides at 6 and 12 weeks while milk MR use was not.

CONCLUSIONS

Soy MR use, as part of a low-energy diet, was associated with slightly but not significantly greater weight loss over a 12-week period than milk MR use. These observations confirm previous studies documenting the effectiveness of MR use for weight loss.