Elsevier

Nutrition

Volume 23, Issues 7–8, July–August 2007, Pages 551-556
Nutrition

Applied nutritional investigation
Effectiveness of a soy-based compared with a traditional low-calorie diet on weight loss and lipid levels in overweight adults

https://doi.org/10.1016/j.nut.2007.05.003Get rights and content

Abstract

Objective

This study investigated the effects of a soy-based low-calorie diet on weight control, body composition, and blood lipid profiles compared with a traditional low-calorie diet.

Methods

Thirty obese adults (mean body mass index 29–30 kg/m2) were randomized to two groups. The soy-based low-calorie group consumed soy protein as the only protein source, and the traditional low-calorie group consumed two-thirds animal protein and the rest plant protein in a 1200 kcal/d diet for 8 wk. A diet record was kept everyday throughout the study. Food intake was analyzed before and after the study. Anthropometric data were acquired every week, and biochemical data from before and after the 8-wk experiment were compared.

Results

Body weight, body mass index, body fat percentage, and waist circumference significantly decreased in both groups (P < 0.05). The decrease in body fat percentage in the soy group (2.2%, 95% confidence interval 1.6–2.8) was greater than that in the traditional group (1.4%, 95% confidence interval −0.1 to 2.8). Serum total cholesterol concentrations, low-density lipoprotein cholesterol concentrations, and liver function parameters decreased in the soy-based group and were significantly different from measurements in the traditional group (P < 0.05). No significant change in serum triacylglycerol levels, serum high-density lipoprotein cholesterol levels, and fasting glucose levels was found in the soy or traditional group.

Conclusion

Soy-based low-calorie diets significantly decreased serum total cholesterol and low-density lipoprotein cholesterol concentrations and had a greater effect on reducing body fat percentage than traditional low-calorie diets. Thus, soy-based diets have health benefits in reducing weight and blood lipids.

Introduction

The prevalence of overweight and obesity worldwide has dramatically increased in recent decades [1]. Compelling evidence has linked obesity not only to various chronic diseases, such as diabetes mellitus, heart disease, hypertension, stroke, cholecystolithiasis, and gout, but also to cancer, including colorectal and breast cancers [2], [3]. In 1996, the World Health Organization and the Food and Agriculture Organization announced that obesity can be regarded as a chronic disease and emphasized the importance of maintaining an ideal body weight. According to results from a survey in Taiwan in 1998 [4], nearly 25% of adults are overweight. This report indicates that obesity has become a serious public health problem in Taiwan. Energy imbalance, i.e., energy intake higher than energy expenditure, is the main reason for people becoming overweight and obese. Dietary patterns are closely related to obesity [5], [6].

Soy contains abundant nutrients and is a common component of the traditional Chinese diet. Soybean proteins are used in a variety of forms, including infant formulas, flours, protein isolates and concentrates, and textured fibers. Soy-containing foods include cheese, drinks, miso, tempeh, tofu, salami, and vegetarian meat substitutes. It has been shown that a soy-based diet has a weight-loss effect and can prevent obesity because soy is rich in dietary fiber, thereby increasing satiety [7], and that a soy-based meal helps to decrease fat mass [8]. Further, soy peptide seems to improve the thermic response of brown adipose tissue and thus may be a useful treatment option for obesity [9], [10]. However, those findings were based on animal studies, and no clinical studies have examined the results of a weight-loss program using soy products for obese people. The effectiveness of soy products on weight loss is still unclear [11]. Therefore, this study investigated the effects of a soy-based diet on weight management and body composition. The results of this study will be applied to clinical therapies for the overweight and obese and to decrease morbidity associated with obesity.

Section snippets

Subjects

This study was carried out at Taipei Medical University. Flyers and leaflets were used to recruit 30 volunteers (6 men and 24 women) before the experiment’s start date. Subjects had to be 20–60 y of age, have a body mass index (BMI) >26 kg/m2, and have no history of chronic disease, including cardiovascular disease, kidney disease, and diabetes mellitus. Female subjects could not be pregnant or breast-feeding. All subjects submitted written informed consent before their participation. The

Results

Thirty subjects (6 men and 24 women) completed the 8-wk intervention study. Fifteen subjects (3 men and 12 women) were assigned to the soy group and 15 subjects (3 men and 12 women) consumed the traditional low-calorie diet. Baseline subject characteristics were similar between groups except age. The traditional group was older than the soy group but there was no significant difference. The initial BMI of subjects given the soy low-calorie diet was 29.6 ± 3.0 kg/m2, and the initial body weight

Discussion

In this study, the effectiveness of weight loss in the soy low-calorie diet group was similar to that in the traditional low-calorie diet group, whereas the body fat percentage of the soy group significantly decreased compared with that of the traditional group. Both groups showed significant decreases in body weight of an average of 0.6 kg/wk, which is within the suggested ideal weight loss rate of 0.5–1 kg/wk [17], [18]. Maskarinec et al. [19] showed that having beans in the diet, including

Acknowledgments

The authors acknowledge Mr. Chin-Fa Chen for providing technical assistance.

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    The American Soy Association provided funding for this project.

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