Eating a healthy balanced diet and exercising more are important for a healthier lifestyle and maintaining a healthy weight. It’s a question of striking the right balance. With increasing numbers of the population being overweight or obese it is crucial that consumers get the right information about how to eat a balanced diet and become more physically active. Soya products can be integrated into an everyday healthy balanced diet. Recent publications underline the role of soya in weight loss.

Effect of soyfoods to maintain a healthy weight
Among all the macronutrients (carbohydrate, fat and protein) protein has the highest suppressing effect on food intake (1). Data indicate that soyfood are as good as other protein sources. In a study of Williamson the satiating effect of soy protein (tofu) as a preload before lunch, was compared to mycoprotein and chicken preload. Mycoprotein and tofu preloads in comparison with chicken preloads, were associated with lower food intake and the participants did not compensate for it at dinner (2).

Effect of soyfoods on weight loss

When considering a calorie-restricted diet, it is important not to compromise the nutrient intake. Soyfood can help to maintain a sufficient nutrient intake. Soyfoods produced from the whole soybean by natural process contain the whole range of nutrients present in the soybean. Soy contains high quality protein and other healthy nutrients such as poly-unsaturated fatty acids, vitamins and minerals and fibres; moreover soyfoods are low in saturated fat.

In studies of Anderson, soyfood as part of a calorie-restricted diet has been shown to be efficient for weight loss in obese patients (3;4).

Liao showed in a recent study that soy-based low calorie diets had a greater effect on reducing body fat percentage than traditional low-calorie diets (5).

Deibert published the results of a 6-months study in 90 pre-obese and obese subjects where a lifestyle education group was compared to a ‘high soy protein/low fat’ diet with or without a physical activity program. The lifestyle education group attended teaching sessions and nutritional counselling and a diet was prescribed. In the ‘high soy protein/low fat’ diet the subjects were instructed to replace some meals with soy and not too exceed a certain amount of fat. The third group was in addition motivated to attend a physical activity program.

BMI dropped in all groups but there was a greater decrease in fat mass in the soy group compared to the lifestyle education group. In addition there was no change in fat-free mass indicating the preservation of muscle mass (6).

In a study of Kohno the effect of beta-conglycinin which is a major component of the soy protein, on visceral fat, was studied. The beta-conglycinin groups showed significant reduction in the visceral fat area while the placebo group showed an increase. Moreover the triglycerides were significantly reduced in the test group (7).

Recent data suggest that also isoflavones, natural plant compounds of soy contribute to a beneficial effect. Wu studied the effect of isoflavone intake of 75 mg/day and exercise (3 times a week) for 1 year in Japanese postmenopausal women. Walking and combined intervention (isoflavone + walking) decreased the body fat mass. Isoflavone intake also reduced significantly fat mass in the trunk region (8).

Aubertin-Leheudre recently published the results of a trial in obese postmenopausal women. The effect of 6 months isoflavone supplementation or placebo was compared to 6 months of exercise and isoflavone or placebo. Compared to an exercise program alone, 70mg of isoflavones combined with exercise resulted in significant changes in body weight, BMI,  total and abdominal fat mass (9).

Beside an increased satiety, other possible mechanism for weight loss with soy mentioned in the literature are a possible thermogenic effect (10;11), an effect on leptin, ghrelin, GLP-1 (glucagon like peptide), insulin and cholecystokinin (12). Further studies are needed to get a better insight on the effect of soy on appetite regulatory peptides, hormones and enzymes.

There is an increasing amount of evidence that indicates that soyfood can be an important element in a healthy diet for maintaining a healthy weight and for weight reduction in overweight and obese persons (13;14).

Soyfoods produced from the whole soybean by natural process contain the whole range of nutrients present in the soybean.

Soy contains high quality protein and other healthy nutrients such as poly-unsaturated fatty acids, vitamins and minerals and fibres; moreover soyfoods are low in saturated fat.

Soyfoods can be included in calorie restricted diets as a high quality protein source.

Overweight and obesity is often accompanied by associated diseases such as dyslipidemia, diabetes, cardiovascular diseases and certain type of cancers.

It is important to know that soy may offer metabolic advantages such as a lipid lowering effect, improvement of insulin resistance and glycemic control.

Soyfoods also fit in a low glycemic load diet which can also have beneficial effect on body mass index.

   1.   Weigle DS, Breen PA, Matthys CC et al. A high-protein diet induces sustained reductions in appetite, ad libitum caloric intake, and body weight despite compensatory changes in diurnal plasma leptin and ghrelin concentrations. Am J Clin Nutr 2005;82:41-8.

    2.   Williamson DA, Geiselman PJ, Lovejoy J et al. Effects of consuming mycoprotein, tofu or chicken upon subsequent eating behaviour, hunger and safety. Appetite 2006;46:41-8.

    3.   Anderson JW, Fuller J, Patterson K, Blair R, Tabor A. Soy compared to casein meal replacement shakes with energy-restricted diets for obese women: randomized controlled trial. Metabolism 2007;56:280-8.

    4.   Anderson JW, Hoie LH. Weight loss and lipid changes with low-energy diets: comparator study of milk-based versus soy-based liquid meal replacement interventions. J Am Coll Nutr 2005;24:210-6.

    5.   Liao FH, Shieh MJ, Yang SC, Lin SH, Chien YW. Effectiveness of a soy-based compared with a traditional low-calorie diet on weight loss and lipid levels in overweight adults. Nutrition 2007;23:551-6.

    6.   Deibert P, Konig D, Schmidt-Trucksaess A et al. Weight loss without losing muscle mass in pre-obese and obese subjects induced by a high-soy-protein diet. Int J Obes Relat Metab Disord 2004;28:1349-52.

    7.   Kohno M, Hirotsuka M, Kito M, Matsuzawa Y. Decreases in Serum Triacylglycerol and Visceral Fat Mediated by Dietary Soybean beta-conglycinin. J Atheroscler Thromb 2006;13:247-55.

    8.   Wu J, Oka J, Tabata I et al. Effects of isoflavone and exercise on BMD and fat mass in postmenopausal Japanese women: a 1-year randomized placebo-controlled trial. J Bone Miner Res 2006;21:780-9.

    9.   Aubertin-Leheudre M, Lord C, Khalil A, Dionne IJ. Effect of 6 months of exercise and isoflavone supplementation on clinical cardiovascular risk factors in obese postmenopausal women: a randomized, double-blind study. Menopause 2007;14:624-9.

 10.   Mikkelsen PB, Toubro S, Astrup A. Effects of fat-reduced diets on 24-h energy expenditure: comparisons between animal protein, vegetable protein, and carbohydrate. Am J Clin Nutr 2000;72:1135-41.

 11.   Claessens M, Calame W, Siemensma AD, Saris WH, van Baak MA. The thermogenic and metabolic effects of protein hydrolysate with or without a carbohydrate load in healthy male subjects. Metabolism 2007;56:1051-9.

 12.   Bowen J, Noakes M, Clifton PM. Appetite regulatory hormone responses to various dietary proteins differ by body mass index status despite similar reductions in ad libitum energy intake. J Clin Endocrinol Metab 2006;91:2913-9.

 13.   Velasquez MT, Bhathena SJ. Role of Dietary Soy Protein in Obesity. Int J Med Sci 2007;4:72-82.

 14.   Cope MB, Erdman JW, Jr., Allison DB. The potential role of soyfoods in weight and adiposity reduction: an evidence-based review. Obes Rev 10207;1-17.