The Role of Soy Protein and Weight Management
Obesity in the United States: A Call for Action
The prevalence of obesity continues to be on the rise in the United States for both adults and children. According to the National Institute of Health (NIH), approximately 65% of American adults are either overweight (Body Mass Index > 25.0) or obese (Body Mass Index equal to or > 30). Over 25% of children and adolescents combined are currently overweight, and this number has been increasing rapidly (NIH, 2000).
The Health Cost of Obesity
The economic cost of obesity in the United States was estimated at $117 billion in 2000 (U.S. Surgeon General's Call to Action, 2001). Obese individuals suffer from numerous adverse health consequences including increased risk for cardiovascular disease, some types of cancers, stroke, diabetes, osteoarthritis, gallbladder disease, sleep apnea and higher mortality rates from all causes than those of normal weight (NHLBI and NIDDK, 1998). Experts say that the medical costs associated with treating these diseases will strain the healthcare system and economy in the years to come (Hellmich, 2003).
Factors that Increase the Risk of Obesity
It is well known that obesity is a complex condition resulting from a variety of factors. These include a combination of family history (genetics), behavioral and environmental factors. Various studies of obesity clearly find that genetic factors predispose specific individuals to develop obesity and its related adverse health risks. Jeffrey Friedman, a scientist at the Howard Hughes Medical Institute at Rockefeller University, says basic differences in an individual's genetics may partly explain why some remain lean in the current environment of fast food and huge portions, while others are hundreds of pounds overweight (Hellmich, 2003). Behavioral and environmental factors that increase the risk for obesity include; an increased sedentary lifestyle, a decrease in physical activity, availability of inexpensive and convenient calorie-dense foods and cultural factors (Hill and Peter, 1998). Other contributing factors may include stage of life, economic status, specific drug initiation (corticosteroids), cigarette smoking cessation and family history of obesity. Some indicate that the large consumption of animal protein in the typical Western diet may be the origin of obesity in the U.S. (McCarthy, 2000).
Weight Loss Trends and Statistics
According to the Calorie Control Council National Surveys, fewer Americans are on diets. Their survey shows that only 24% of U.S. adults (51 million people) are currently dieting compared to 37% in 1986. Although 47% (124 million people) are reported to be making a conscious effort to control their weight, waistlines continue to grow.
The number one reason in the survey given for weight loss failure is a lack of exercise (50% of respondents). Other top reasons include frequent splurging on favorite foods (36% of respondents), too much snacking (33% of respondents), and respondents claiming that they eat too many high-fat foods and eat for emotional reasons (28%).(Calorie Control Council, 2003).
Americans may be getting the message that short-term diet measures just don't work. This is evident in that approximately two thirds of dieters have lost at least ten pounds in recent months, according to the study. "Pills, fad diets and cutting out certain food groups just aren't working and consumers are finally realizing this. To loose pounds, you've basically got to lighten up and also get moving", said Lynn O'Brien Nabors, Executive Vice President of the Calorie Control Council.
Weight Reduction: The Controversy of Dietary Composition
There are a multitude of diets proclaiming the benefits or risks of carbohydrates (CHO) versus protein or fat for weight loss. However, the ideal ratio of CHO to protein for weight management and adult health is inconclusive. Additionally, the optimal balance of all macronutrients (CHO, fat and protein) for controlling obesity is at the center of debate (Laymen et al, 2003)
Changes in body composition and weight require changes in energy intake (calories consumed) and energy expenditure (calories burned). Acceptable Macronutrient Distribution Ranges (AMDRs) for adults are 20 - 35% fat, 45 - 65% carbohydrates and 10 - 35% protein. (Institutes of Medicine, 2002).
Diets high in some carbohydrates (simple and refined) can cause a rapid rise in blood sugar leading to a period of hypoglycemia (low blood sugar) and increased hunger. Diets high in protein, namely animal protein, have been termed ˇ°atherogenicˇ± or increasing the risk of heart disease. This is due to their higher levels of fat, saturated fat and cholesterol than the typical high CHO diet. Although not any one diet works for everyone, recent studies suggest that changes in the ratio of protein (animal) to carbohydrates toward a higher protein diet can improve body composition and blood lipids during weight loss in adult women ( Laymen et al, 2003 ).
The Role of Soy Protein and Weight Reduction
Soy Protein: High Quality Protein
Calorie-restricted diets require adequate, high quality protein for muscle repair and synthesis and lean muscle tissue maintenance. Various findings show that well processed soy protein isolates and concentrates can serve as the major or even sole source of protein intake and that their protein values are essentially equivalent to that of foods of animal protein (Young, 1991).
Soybeans are the only vegetable that contains complete protein. Soybean protein provides all eight essential amino acids in the amounts needed for human health. Additionally, the amino acid profile of soy protein is essentially equivalent in protein quality to that of milk, meat and egg protein.
Soy Protein and Weight Loss
Soy protein contains all eight essential amino acids. It is also higher in non-essential amino acids than the majority of animal proteins. Some researchers feel that proteins higher in non-essential amino acids should preferentially favor glucagon production (fat burning) and decrease insulin secretion (McCarthy, 1999). Moreover, protein from legumes (soy and others) may be more slowly absorbed, as compared to animal protein. (McCarthy, 2000). In single meal tests, protein exhibited a greater thermogenic (heat producing) and satiating effect than carbohydrate (Mikkelsen et al., 2000). This means that soy protein produces a larger calorie expenditure than carbohydrate. In fact, substitution of carbohydrate with 17-18% of energy as either pork-meat or soy protein produced a 3% higher 24- hour energy expenditure, which may serve as a preventative measure in the treatment of obesity (Mikkelsen et al.,2000).
Isolated soy protein provokes a greater release of the hormone glucagon. Glucagon is responsible for the obstruction of fat storing enzymes and increasing fat metabolism (fat burning). It is also responsible for decreasing cholesterol synthesis (production). Thus, diets featuring vegan (plant) proteins can be expected to lower elevated serum lipid levels (triglycerides and cholesterol), and promote weight loss. Bosello et al, (1988), Jenkins et al (1989), McCarthy (1999).
Weight loss, especially when seen from very low calorie diets, promotes fat and lean muscle tissue loss. Researchers have reported increases in lean body mass in peri-menopausal (before menopause) women when soy protein and not animal protein was used as the dietary source of protein. (Moeller et al, 2000). Animal studies have also shown the beneficial effects of soy protein on weight reduction. (Arjmandi et al., 1996).
In another animal study by Aoyama et al (2000), weight and body fat reduction in rats and mice subjects was more dramatic when fed a diet of soy protein isolate compared to those fed a casein-based diet. It was concluded that these results indicate that soy protein isolate is a suitable protein source in an energy-restricted diet for treating obesity.
Soy Protein: Improved Glucose Control
Soy protein and its many bioactive components may play a beneficial role in obesity and diabetes. Small, short-term human and animal studies with obese, diabetic and non-diabetic subjects have shown positive effects on weight loss, and reduction in blood lipids, insulin and insulin resistance (Bhathena et al, 2002). In a study by Aoyama et al (2000), rats fed a diet of soy protein had lower plasma glucose levels than those fed the casein diets. It is not clear which component of soy is responsible for these effects. However, it appears that soy and its bioactive components may help to regulate insulin secretion.
References
The prevalence of obesity continues to be on the rise in the United States for both adults and children. According to the National Institute of Health (NIH), approximately 65% of American adults are either overweight (Body Mass Index > 25.0) or obese (Body Mass Index equal to or > 30). Over 25% of children and adolescents combined are currently overweight, and this number has been increasing rapidly (NIH, 2000).
The Health Cost of Obesity
The economic cost of obesity in the United States was estimated at $117 billion in 2000 (U.S. Surgeon General's Call to Action, 2001). Obese individuals suffer from numerous adverse health consequences including increased risk for cardiovascular disease, some types of cancers, stroke, diabetes, osteoarthritis, gallbladder disease, sleep apnea and higher mortality rates from all causes than those of normal weight (NHLBI and NIDDK, 1998). Experts say that the medical costs associated with treating these diseases will strain the healthcare system and economy in the years to come (Hellmich, 2003).
Factors that Increase the Risk of Obesity
It is well known that obesity is a complex condition resulting from a variety of factors. These include a combination of family history (genetics), behavioral and environmental factors. Various studies of obesity clearly find that genetic factors predispose specific individuals to develop obesity and its related adverse health risks. Jeffrey Friedman, a scientist at the Howard Hughes Medical Institute at Rockefeller University, says basic differences in an individual's genetics may partly explain why some remain lean in the current environment of fast food and huge portions, while others are hundreds of pounds overweight (Hellmich, 2003). Behavioral and environmental factors that increase the risk for obesity include; an increased sedentary lifestyle, a decrease in physical activity, availability of inexpensive and convenient calorie-dense foods and cultural factors (Hill and Peter, 1998). Other contributing factors may include stage of life, economic status, specific drug initiation (corticosteroids), cigarette smoking cessation and family history of obesity. Some indicate that the large consumption of animal protein in the typical Western diet may be the origin of obesity in the U.S. (McCarthy, 2000).
Weight Loss Trends and Statistics
According to the Calorie Control Council National Surveys, fewer Americans are on diets. Their survey shows that only 24% of U.S. adults (51 million people) are currently dieting compared to 37% in 1986. Although 47% (124 million people) are reported to be making a conscious effort to control their weight, waistlines continue to grow.
The number one reason in the survey given for weight loss failure is a lack of exercise (50% of respondents). Other top reasons include frequent splurging on favorite foods (36% of respondents), too much snacking (33% of respondents), and respondents claiming that they eat too many high-fat foods and eat for emotional reasons (28%).(Calorie Control Council, 2003).
Americans may be getting the message that short-term diet measures just don't work. This is evident in that approximately two thirds of dieters have lost at least ten pounds in recent months, according to the study. "Pills, fad diets and cutting out certain food groups just aren't working and consumers are finally realizing this. To loose pounds, you've basically got to lighten up and also get moving", said Lynn O'Brien Nabors, Executive Vice President of the Calorie Control Council.
Weight Reduction: The Controversy of Dietary Composition
There are a multitude of diets proclaiming the benefits or risks of carbohydrates (CHO) versus protein or fat for weight loss. However, the ideal ratio of CHO to protein for weight management and adult health is inconclusive. Additionally, the optimal balance of all macronutrients (CHO, fat and protein) for controlling obesity is at the center of debate (Laymen et al, 2003)
Changes in body composition and weight require changes in energy intake (calories consumed) and energy expenditure (calories burned). Acceptable Macronutrient Distribution Ranges (AMDRs) for adults are 20 - 35% fat, 45 - 65% carbohydrates and 10 - 35% protein. (Institutes of Medicine, 2002).
Diets high in some carbohydrates (simple and refined) can cause a rapid rise in blood sugar leading to a period of hypoglycemia (low blood sugar) and increased hunger. Diets high in protein, namely animal protein, have been termed ˇ°atherogenicˇ± or increasing the risk of heart disease. This is due to their higher levels of fat, saturated fat and cholesterol than the typical high CHO diet. Although not any one diet works for everyone, recent studies suggest that changes in the ratio of protein (animal) to carbohydrates toward a higher protein diet can improve body composition and blood lipids during weight loss in adult women ( Laymen et al, 2003 ).
The Role of Soy Protein and Weight Reduction
Soy Protein: High Quality Protein
Calorie-restricted diets require adequate, high quality protein for muscle repair and synthesis and lean muscle tissue maintenance. Various findings show that well processed soy protein isolates and concentrates can serve as the major or even sole source of protein intake and that their protein values are essentially equivalent to that of foods of animal protein (Young, 1991).
Soybeans are the only vegetable that contains complete protein. Soybean protein provides all eight essential amino acids in the amounts needed for human health. Additionally, the amino acid profile of soy protein is essentially equivalent in protein quality to that of milk, meat and egg protein.
Soy Protein and Weight Loss
Soy protein contains all eight essential amino acids. It is also higher in non-essential amino acids than the majority of animal proteins. Some researchers feel that proteins higher in non-essential amino acids should preferentially favor glucagon production (fat burning) and decrease insulin secretion (McCarthy, 1999). Moreover, protein from legumes (soy and others) may be more slowly absorbed, as compared to animal protein. (McCarthy, 2000). In single meal tests, protein exhibited a greater thermogenic (heat producing) and satiating effect than carbohydrate (Mikkelsen et al., 2000). This means that soy protein produces a larger calorie expenditure than carbohydrate. In fact, substitution of carbohydrate with 17-18% of energy as either pork-meat or soy protein produced a 3% higher 24- hour energy expenditure, which may serve as a preventative measure in the treatment of obesity (Mikkelsen et al.,2000).
Isolated soy protein provokes a greater release of the hormone glucagon. Glucagon is responsible for the obstruction of fat storing enzymes and increasing fat metabolism (fat burning). It is also responsible for decreasing cholesterol synthesis (production). Thus, diets featuring vegan (plant) proteins can be expected to lower elevated serum lipid levels (triglycerides and cholesterol), and promote weight loss. Bosello et al, (1988), Jenkins et al (1989), McCarthy (1999).
Weight loss, especially when seen from very low calorie diets, promotes fat and lean muscle tissue loss. Researchers have reported increases in lean body mass in peri-menopausal (before menopause) women when soy protein and not animal protein was used as the dietary source of protein. (Moeller et al, 2000). Animal studies have also shown the beneficial effects of soy protein on weight reduction. (Arjmandi et al., 1996).
In another animal study by Aoyama et al (2000), weight and body fat reduction in rats and mice subjects was more dramatic when fed a diet of soy protein isolate compared to those fed a casein-based diet. It was concluded that these results indicate that soy protein isolate is a suitable protein source in an energy-restricted diet for treating obesity.
Soy Protein: Improved Glucose Control
Soy protein and its many bioactive components may play a beneficial role in obesity and diabetes. Small, short-term human and animal studies with obese, diabetic and non-diabetic subjects have shown positive effects on weight loss, and reduction in blood lipids, insulin and insulin resistance (Bhathena et al, 2002). In a study by Aoyama et al (2000), rats fed a diet of soy protein had lower plasma glucose levels than those fed the casein diets. It is not clear which component of soy is responsible for these effects. However, it appears that soy and its bioactive components may help to regulate insulin secretion.
References
- Aoyama T, Fukui K, Takamatsu K, Hashimoto Y, Yamamoto T. Soy protein isolate and its hydrolysate reduce body fat of dietary obese rats and genetically obese mice (yellow KK). Nutrition 2000;16(5):349-54.
- Arjmandi BH, Alekel L, Hollis BW, et al. Dietary soybean protein prevents bone loss in an ovariectomized rat model of osteoporosis. J Nutr 1996;126:161-67.
- Bhathena S, Velasquez M. Beneficial role of dietary phytoestrogens in obesity and diabetes. American Journal of Clinical Nutrition 2002; 76(6):1191-1201.
- Bosello O, Cominacini L, Zocca I, et al. Short-and long-term effect of hypocaloric diets containing proteins of different sources on plasma lipids and apoproteins of obese subjects. Ann Nutr Metab 1988;32:206-14.
- Calorie Control Council. Calorie Control National Surveys. www.caloriecontrol.org 2002.
- Hellmich N. Obesity rate could reach nearly 40% in five years. USA Today; February 7, 2003(4A).
- Hill Jo, Peters JC. Environmental contributions to the obesity epidemic. Science 1998;280:1371-74.
- Institute of Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein and Amino Acids (Macronutrients), 2002.
- Jenkins DJA, Wolever TMS, Spiller G, et al. Hypocholesterolemic effect of vegetable protein in a hypocaloric diet. Athersclerosis 1989;78:99-107.
- Layman D, Boileau R, Erickson D, Painter J, Shiue H, Sather C, Christou D. A reduced ratio of dietary carbohydrate to protein improves body composition and blood lipid profiles during weight loss in adult women. J Nutr 2003;133:411-417.
- McCarthy MF. Vegan proteins may reduce risk of cancer, obesity, and cardiovascular disease by promoting increased glucagons activity. Med Hypotheses 1999;53(6);459-85.
- McCarthy MF. The origins of western obesity: a role for animal protein? Med Hypotheses 2000;54(3):488-94.
- Mikkelsen, B, Toubro S, Astrup A. Effect of fat-reduced diets on 24-h energy expenditure: comparisons between animal protein, vegetable protein, and carbohydrate. American Journal of Clinical Nutrition 2000; 72(5):1135-1141.
- Moeller LE, Peterson CT, Hanson KB, et al. Isoflavone-rich soy favorably affects regional fat and lean tissue in menopausal women. FASEB 2000;348.4 A487.
- NIH, NHLBI, NAASO. The Practical Guide; Identification, Evaluation, and Treatment of Overweight and Obesity in Adults. October 2000.
- Young VR. Soy protein in relation to human protein and amino acid nutrition. J Am Diet Assoc. 1991;91(7):828-35.