Bean Institute

By Elizabeth A. Rondini, PhD, RD and Jenifer I. Fenton, PhD, MPH

Obesity continues to be a significant public health concern on a global basis.  In 2005, the World Health Organization estimated that more than one billion adults were overweight (body mass index [BMI] > 25) and 400 million considered obese (BMI > 30) (1).  In the U.S. approximately 70% of adults are now classified as either being overweight or obese (2).  Excess body fat, particularly in the abdominal region, is associated with a number of health consequences including increased risk for type 2 diabetes, cardiovascular disease, hypertension, stroke, and certain types of cancer (1,3).  It is estimated that approximately 400,000 deaths per year in the U.S. are attributed to overweight and obesity (4), with associated medical costs as high as $78 billion per year (5). The increased prevalence in childhood obesity is even more disturbing, as overweight children are more likely to be obese as adults and face a higher risk for premature death and disability (1,6,7).

Obesity is thought to develop from the interaction of both genetic and environmental factors (8), however increasing physical activity and reducing energy intake are generally accepted measures to decrease one’s chances of becoming obese.  Hypocaloric, low fat (<30% kilocalories) diets are often recommended for managing body weight as well as metabolic risk factors associated with obesity (3).  However, decreasing the amount of dietary fat often leads to a concomitant increase in energy intake from carbohydrates.  Along with the increasing prevalence of obesity and type 2 diabetes, total energy as well as the percent of energy from carbohydrates has increased, particularly from more refined, low fiber sources (9-12).  This has led to the suggestion that the amount and type of carbohydrates consumed may influence food and energy intake, thereby regulating body weight gain (13-15).

GI and Body Weight
One potential mechanism whereby carbohydrate-containing foods may influence body weight is related to the rate which glucose and insulin appear in the blood following a meal.  The glycemic index (GI) measures the extent to which a test food increases blood glucose over a period of 2 hours compared to eating an equivalent amount of carbohydrate from either glucose or white bread (16-18).  Foods with a high GI cause a more rapid rise in blood glucose and insulin levels than foods with a low GI.  Because the extent to which different foods raise blood glucose also depends on the quantity of carbohydrates consumed, the term glycemic load (GL) was introduced (19).  The GL is calculated by multiplying the individual GIs of each food by the quantity of available carbohydrate eaten.  Many factors can influence the glycemic response of foods including the nature of the starch, cooking methods, as well as the amount of fat, protein, and dietary fiber (20-22).  However, in general, standard servings of non-starchy vegetables, legumes, and fruits produce lower glycemic responses compared to more refined grains and potatoes (13) .

Consumption of low GI/GL food sources may benefit weight control by more favorably affecting metabolic and hormonal profiles after a meal, leading to increased satiety and reduced propensity for hunger (13,23-25).  A majority of short-term feeding studies reported a delay in return of hunger, increased satiety, and/or reduced voluntary food intake at subsequent meals when low compared to high GI/GL foods were consumed (13,23).  Two systemic reviews compared the long term efficacy of dietary GI on body weight regulation (26,27).  Thomas et al (27) analyzed randomized control studies conducted in non-diabetic, overweight or obese individuals in which dietary intervention was greater than 5 weeks duration.  They found that low GI/GL diets were associated with significant reductions in body weight (1.1 kg), fat mass (1.1 kg), and BMI (1.3 units) when compared to high glycemic or conventional, reduced energy diets.  A more beneficial effect of low GI diets on body weight was found in obese individuals.  Livesey et al. (26) evaluated the relationship between gylcemic response and markers of health.  They found that low GI/GL diets were significantly associated with lower body weights under free living conditions and when food intake control is limited (26).  Reducing the GL resulted in less available carbohydrate intake (therefore fewer kilocalories) leading to more weight loss, although there was a threshold before these effects occurred.  Additional benefits of low GI/GL, high fiber diets were seen for blood glucose, insulin sensitivity, and fasting blood triglyceride levels.

Although the effect of lowering dietary GI/GL alone on body weight appears modest, more recent studies suggest that an individual’s insulin response at 30 minutes (insulin-30) following a glucose challenge is a better predictor of weight loss on low GI/GL diets and may account for some of the variation between studies (28,29).  Consumption of low glycemic diets may also complement lifestyle interventions for weight loss (30).  In obese individuals, combining low glycemic diets with aerobic exercise for 12 weeks had a synergistic effect on weight loss and in improving insulin sensitivity and plasma triglycerides (30).  Collectively these studies suggest that consumption of low glycemic carbohydrate sources (GI < 45), a low glycemic load (<100 g equivalents per day), and at least 25 g per day of dietary fiber would likely benefit individuals by helping them to consume fewer kilocalories, thereby reducing body weight and improving metabolic risk factors associated with obesity (26).

Beans and Body Weight
Increasing consumption of legumes (peas, beans, lentils, peanuts) to 3 cups per week is recommended as a part of the Dietary Guidelines for Americans to promote health and reduce risk of chronic disease (31).  However despite these recommendations, overall intake of legumes in the U.S. remains low (32,33).  The incorporation of beans into the standard U.S. diet in place of more high GI carbohydrate sources may have clinical value in the management of obesity.  Compared to other carbohydrate sources, dry beans have a relatively low glycemic index, varying from 27-42% relative to glucose and 40-59% that of white bread (34).  Additionally 1/2 cup of cooked beans provides ~2 g of soluble dietary fiber, which has been associated with delayed gastric emptying and a more sustained increase in glucose and insulin levels.  Higher intakes of dietary fiber are also associated with improved glycemic control (35-37), lower blood cholesterol (37-41), as well as reduced body fat (37,42-44).

Limited evidence suggests that increasing consumption of beans may be advantageous in managing body weight.  In a short-term feeding study, bean consumption resulted in greater satiety after a meal and delayed the return of hunger compared to a high GI food source (45).  In epidemiology studies, legume intake evaluated as part of a healthy diet pattern was associated with lower energy intakes (46), reduced waist circumferences (46-48), and/or lower BMIs (47-49).  Papanikolaou et al. (50) specifically examined the influence of bean consumption on body weight and cardiovascular disease risk factors in adults from the National Health and Nutrition Examination Survey (1999-2002).  They reported that bean consumers in general had better nutrient profiles for dietary fiber as well as several key micronutrients including potassium, magnesium, iron, and copper.  Regular consumers of beans also had significantly lower body weights (77.5 ± 1.1 vs. 80.5 ± 0.3 kg), smaller waist size (94.2 ± 1.0 vs. 96.1 ± 0.3 cm), and a trend towards lower systolic blood pressure.  This was associated with a 22% less chance of being obese.  Legume intake may also aid in nutritional interventions for weight loss (51).  Abete et al (51) studied the effect of hypocaloric diets (30% restriction in energy) with legumes (4 servings/week) compared to a control, macronutrient-matched diet on weight loss in obese males.  Consumption of a high legume diet for 8 weeks was associated with significantly more body weight loss (-8.3% ± 2.9 vs. -5.5% ± 2.5) and a greater reduction in systolic blood pressure compared to individuals on the control diet.  In addition, legumes reduced LDL (-25.5% ± 11.8) and total cholesterol (-19.5% ± 9.3) compared to baseline values.

Bottom Line
Collectively, available evidence suggests that low glycemic/high fiber containing foods such as beans, can impact metabolic profiles associated with obesity and may be an effective dietary measure to aid in weight loss and/or maintenance.  Evidence specifically linking consumption of beans to body weight is limited.  However some benefits may be achieved in lowering cholesterol and blood pressure as well as maintaining glycemic control.

About the Authors

References

1.    World Health Organization (WHO) (2006) Obesity and overweight fact sheet. http://www.who.int/mediacentre/factsheets/fs311/en/index.html.
2.    Flegal KM, Carroll MD, Ogden CL, et al. (2010) Prevalence and Trends in Obesity Among US Adults, 1999-2008. JAMA; 303: 235-241.
3.    National Institutes of Health (NIH) NHLBI (1998) Obesity Education Initiative. Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults. . http://www.nhlbi.nih.gov/guidelines/obesity/ob_gdlns.pdf.
4.    Mokdad AH, Marks JS, Stroup DF, et al. (2004) Actual causes of death in the United States, 2000. Jama; 291: 1238-45.
5.    Finkelstein EA, Fiebelkorn IC, Wang G (2003) National medical spending attributable to overweight and obesity: how much, and who’s paying? Health Aff (Millwood); Suppl Web Exclusives: W3-219-26.
6.    Serdula MK, Ivery D, Coates RJ, et al. (1993) Do obese children become obese adults? A review of the literature. Prev Med; 22: 167-77.
7.    Whitaker RC, Wright JA, Pepe MS, et al. (1997) Predicting obesity in young adulthood from childhood and parental obesity. N Engl J Med; 337: 869-73.
8.    Shuldiner AR, Munir KM (2003) Genetics of obesity: more complicated than initially thought. Lipids; 38: 97-101.
9.    Chanmugam P, Guthrie JF, Cecilio S, et al. (2003) Did fat intake in the United States really decline between 1989-1991 and 1994-1996? J Am Diet Assoc; 103: 867-72.
10.    Harnack LJ, Jeffery RW, Boutelle KN (2000) Temporal trends in energy intake in the United States: an ecologic perspective. Am J Clin Nutr; 71: 1478-84.
11.    Putnam J, Allshouse J, Kantor LS (2002) U.S. per capita food supply trends. Food Review[USDA]; 25(3); http://www.ers.usda.gov/publications/FoodReview/DEC2002/frvol25i3a.pdf.
12.    Gross LS, Li L, Ford ES, et al. (2004) Increased consumption of refined carbohydrates and the epidemic of type 2 diabetes in the United States: an ecologic assessment. Am J Clin Nutr; 79: 774-9.
13.    Ludwig DS (2000) Dietary glycemic index and obesity. J Nutr; 130: 280S-283S.
14.    Ludwig DS (2002) The glycemic index: physiological mechanisms relating to obesity, diabetes, and cardiovascular disease. Jama; 287: 2414-23.
15.    Ludwig DS (2003) Dietary glycemic index and the regulation of body weight. Lipids; 38: 117-21.
16.    Jenkins DJ, Wolever TM, Taylor RH, et al. (1981) Glycemic index of foods: a physiological basis for carbohydrate exchange. Am J Clin Nutr; 34: 362-6.
17.    Wolever TM, Jenkins DJ, Jenkins AL, et al. (1991) The glycemic index: methodology and clinical implications. Am J Clin Nutr; 54: 846-54.
18.    Ludwig DS, Majzoub JA, Al-Zahrani A, et al. (1999) High glycemic index foods, overeating, and obesity. Pediatrics; 103: E26.
19.    Salmeron J, Ascherio A, Rimm EB, et al. (1997) Dietary fiber, glycemic load, and risk of NIDDM in men. Diabetes Care; 20: 545-50.
20.    Jenkins DJA, Kendall CWC, Augustin LSA, et al. (2002) Glycemic index: overview of implications in health and disease. American Journal of Clinical Nutrition; 76: 266S-273S.
21.    Krezowski PA, Nuttall FQ, Gannon MC, et al. (1986) The effect of protein ingestion on the metabolic response to oral glucose in normal individuals. Am J Clin Nutr; 44: 847-56.
22.    Thorne MJ, Thompson LU, Jenkins DJ (1983) Factors affecting starch digestibility and the glycemic response with special reference to legumes. Am J Clin Nutr; 38: 481-8.
23.    Bornet FR, Jardy-Gennetier AE, Jacquet N, et al. (2007) Glycaemic response to foods: impact on satiety and long-term weight regulation. Appetite; 49: 535-53.
24.    Brand-Miller JC, Holt SHA, Pawlak DB, et al. (2002) Glycemic index and obesity. American Journal of Clinical Nutrition; 76: 281S-285S.
25.    Jenkins DJ, Kendall CW, Augustin LS, et al. (2002) Glycemic index: overview of implications in health and disease. Am J Clin Nutr; 76: 266S-73S.
26.    Livesey G, Taylor R, Hulshof T, et al. (2008) Glycemic response and health–a systematic review and meta-analysis: relations between dietary glycemic properties and health outcomes. Am J Clin Nutr; 87: 258S-268S.
27.    Thomas DE, Elliott EJ, Baur L (2007) Low glycaemic index or low glycaemic load diets for overweight and obesity. Cochrane Database Syst Rev; CD005105.
28.    Chaput JP, Tremblay A, Rimm EB, et al. (2008) A novel interaction between dietary composition and insulin secretion: effects on weight gain in the Quebec Family Study. Am J Clin Nutr; 87: 303-9.
29.    Ebbeling CB, Leidig MM, Feldman HA, et al. (2007) Effects of a low-glycemic load vs low-fat diet in obese young adults: a randomized trial. Jama; 297: 2092-102.
30.    Kirwan JP, Barkoukis H, Brooks LM, et al. (2009) Exercise training and dietary glycemic load may have synergistic effects on insulin resistance in older obese adults. Ann Nutr Metab; 55: 326-33.
31.    U.S. Department of Health and Human Services, U.S. Department of Agriculture (2005) Dietary Guidelines for Americans. http://www.health.gov/dietaryguidelines/dga2005/document/html/chapter5.htm.
32.    Kimmons J, Gillespie C, Seymour J, et al. (2009) Fruit and vegetable intake among adolescents and adults in the United States: percentage meeting individualized recommendations. Medscape J Med; 11: 26.
33.    Messina MJ (1999) Legumes and soybeans: overview of their nutritional profiles and health effects. Am J Clin Nutr; 70: 439S-450S.
34.    Foster-Powell K, Miller JB (1995) International tables of glycemic index. Am J Clin Nutr; 62: 871S-890S.
35.    Sievenpiper JL, Kendall CW, Esfahani A, et al. (2009) Effect of non-oil-seed pulses on glycaemic control: a systematic review and meta-analysis of randomised controlled experimental trials in people with and without diabetes. Diabetologia; 52: 1479-95.
36.    Anderson JW, Randles KM, Kendall CW, et al. (2004) Carbohydrate and fiber recommendations for individuals with diabetes: a quantitative assessment and meta-analysis of the evidence. J Am Coll Nutr; 23: 5-17.
37.    Anderson JW, Baird P, Davis RH, Jr., et al. (2009) Health benefits of dietary fiber. Nutr Rev; 67: 188-205.
38.    Anderson JW, Major AW (2002) Pulses and lipaemia, short- and long-term effect: potential in the prevention of cardiovascular disease. Br J Nutr; 88 Suppl 3: S263-71.
39.    Bazzano LA, Thompson AM, Tees MT, et al. (2009) Non-soy legume consumption lowers cholesterol levels: A meta-analysis of randomized controlled trials. Nutr Metab Cardiovasc Dis; ISSN 1590-3729 (Electronic):
40.    Brown L, Rosner B, Willett WW, et al. (1999) Cholesterol-lowering effects of dietary fiber: a meta-analysis. Am J Clin Nutr; 69: 30-42.
41.    Wei ZH, Wang H, Chen XY, et al. (2009) Time- and dose-dependent effect of psyllium on serum lipids in mild-to-moderate hypercholesterolemia: a meta-analysis of controlled clinical trials. Eur J Clin Nutr; 63: 821-7.
42.    Slavin JL (2005) Dietary fiber and body weight. Nutrition; 21: 411-8.
43.    Tucker LA, Thomas KS (2009) Increasing total fiber intake reduces risk of weight and fat gains in women. J Nutr; 139: 576-81.
44.    Maskarinec G, Takata Y, Pagano I, et al. (2006) Trends and dietary determinants of overweight and obesity in a multiethnic population. Obesity (Silver Spring); 14: 717-26.
45.    Leathwood P, Pollet P (1988) Effects of slow release carbohydrates in the form of bean flakes on the evolution of hunger and satiety in man. Appetite; 10: 1-11.
46.    Ledikwe JH, Smiciklas-Wright H, Mitchell DC, et al. (2004) Dietary patterns of rural older adults are associated with weight and nutritional status. J Am Geriatr Soc; 52: 589-95.
47.    Newby PK, Muller D, Hallfrisch J, et al. (2004) Food patterns measured by factor analysis and anthropometric changes in adults. Am J Clin Nutr; 80: 504-13.
48.    Cunha DB, de Almeida RM, Sichieri R, et al. Association of dietary patterns with BMI and waist circumference in a low-income neighbourhood in Brazil. Br J Nutr; 1-6.
49.    Sichieri R (2002) Dietary patterns and their associations with obesity in the Brazilian city of Rio de Janeiro. Obes Res; 10: 42-8.
50.    Papanikolaou Y, Fulgoni VL, 3rd (2008) Bean consumption is associated with greater nutrient intake, reduced systolic blood pressure, lower body weight, and a smaller waist circumference in adults: results from the National Health and Nutrition Examination Survey 1999-2002. J Am Coll Nutr; 27: 569-76.
51.    Abete I, Parra D, Martinez JA (2009) Legume-, fish-, or high-protein-based hypocaloric diets: effects on weight loss and mitochondrial oxidation in obese men. J Med Food; 12: 100-8.