The escalating rates of overweight and obesity constitute a significant global health challenge. This surge elevates the risk of various non-communicable diseases and diminishes overall life quality. While a balanced diet and regular exercise are fundamental in addressing obesity, their effectiveness can be limited due to adherence challenges and compensatory changes in energy balance. Although some weight-loss therapies exist, they often come with side effects and high costs. White kidney bean extract (WKBE) has emerged as a potential alternative or supplementary approach. It is believed to inhibit the α-amylase enzyme, thereby reducing carbohydrate digestion and absorption, which may lead to beneficial effects on body weight and metabolic health. This article explores the existing evidence from both human and animal studies regarding the impact of WKBE on body composition and metabolic health.
The Global Obesity Pandemic
The world faces an obesity pandemic, with prevalence tripling since 1975. In 2016, over 1.9 billion adults were overweight, with 650 million classified as obese. Childhood obesity is also rising, with 41 million children overweight or obese in 2016. Obesity and its related conditions, such as type 2 diabetes and cardiovascular disease, pose a substantial burden on public health services and economies worldwide. Overweight and obesity were responsible for approximately 4 million deaths globally in 2015. The issue, once confined to high-income countries, is now rapidly increasing in low-income nations. Obesity results from a chronic energy imbalance, where energy intake surpasses expenditure.
Traditional and Alternative Weight-Loss Strategies
Weight loss, the primary focus of obesity treatment, can be achieved through lifestyle adjustments (diet and exercise), pharmacological interventions, or surgical procedures. Lifestyle interventions aim to create a negative energy balance by reducing caloric intake and increasing physical activity. Combining diet and exercise has been shown to reduce body weight and fat while increasing fat-free mass compared to diet alone. However, implementing lifestyle changes can be challenging due to reliance on participant compliance, and maintaining long-term adherence and weight loss is difficult. Additionally, these interventions often yield smaller-than-expected reductions in body fat and weight due to compensatory changes in energy balance.
Pharmacological agents, like Orlistat, can aid weight loss by inhibiting fat absorption. However, their use is limited by side effects. Some pharmacological treatments have been withdrawn due to adverse effects, such as increased risk of psychiatric events or cardiovascular disease. Surgical interventions, such as bariatric surgery, can achieve significant weight loss in severe cases. However, they require a commitment to permanent lifestyle and dietary changes post-surgery.
Bioactive compounds from food sources offer a promising alternative or adjunct to traditional weight-loss strategies. These compounds can be easily incorporated into habitual diets, are typically inexpensive, and have a low risk of adverse events.
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The Role of Alpha-Amylase and White Kidney Beans
Alpha-amylase, an enzyme crucial in carbohydrate metabolism, facilitates the breakdown of starch and oligosaccharides. Inhibiting this enzyme presents a potential target for interventions aimed at reducing carbohydrate uptake. White kidney beans (Phaseolus vulgaris L.) contain three α-amylase inhibitor isoforms-α-AI1, α-AI2, α-AIL-with α-AI1 inhibiting amylase activity in mammals. α-AI1 interacts with pancreatic α-amylase at its active site, competitively inhibiting its binding with carbohydrates, blocking the enzyme’s substrate-reducing end and obstructing the non-substrate-reducing end through steric hindrance.
Commercially available WKBEs contain high quantities of α-amylase inhibitors derived from white kidney beans. These supplements claim to reduce carbohydrate absorption and digestion, leading to beneficial effects on body weight and metabolic health. While meta-analyses have explored these claims, they either predate recent research or focus on specific brands, potentially overlooking the differential effectiveness of other WKBE formulations.
Animal Studies: WKBE and Body Composition
Animal studies, lasting from 14 to 238 days, have investigated the effects of WKBE on body weight and composition. While not universally consistent, several studies have shown significant reductions in body weight or reduced weight gain with WKBE administration compared to controls. For example, mice supplemented with WKBE alongside a high-fat diet experienced attenuated weight gain and reduced visceral fat. Similarly, mice with diet-induced metabolic syndrome supplemented with WKBE gained less weight than control groups.
Recent research suggests that the anti-obesity effects of WKBE may depend on both dose and duration. Rats receiving higher doses of WKBE for longer durations showed significant reductions in body weight, intra-abdominal fat, and improved blood lipid profiles. These effects may stem from a lower food efficiency ratio, indicating reduced energy absorption from food, and potentially an anorexigenic effect of WKBE. However, not all studies have reported weight reduction with WKBE supplementation. Disparities may arise from differences in supplement activity, purity, dose, duration, animal health status, breed, and research quality. Furthermore, the translation of animal findings to humans requires careful consideration, especially given the complex etiology of obesity.
Impact of WKBE on Blood Biochemistry in Animal Models
Studies on animals have primarily focused on blood glucose, triglycerides, and cholesterol. Both mice and rats, when supplemented with various WKBEs at doses ranging from 500 mg/kg to 4 g/kg, showed improvements in blood glucose levels compared to control groups. However, some studies did not observe corresponding improvements in plasma insulin levels despite reductions in blood glucose. In a diet-induced obesity mouse model, WKBE reduced circulating triglycerides, total cholesterol, and LDL cholesterol compared to a high-fat diet alone. These findings were accompanied by significant reductions in serum glucose, insulin, and HOMA-IR, indicating improved insulin sensitivity.
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Human Clinical Trials: Assessing the Efficacy of WKBE
The effectiveness of WKBE in humans has been evaluated through numerous clinical trials, with varying results. Some studies suggest that WKBE can significantly reduce body weight, fat mass, and waist circumference. However, other studies report no significant impact on these parameters. These conflicting results may be due to differences in study design, dosage, the specific WKBE used, and the characteristics of the participants.
One 14-week double-blind, randomized, placebo-controlled trial investigated the effects of a specific WKBE (Phase 2) on overweight and moderately obese individuals. Participants were instructed to maintain a balanced, hypocaloric diet and were given either a high dose of Phase 2 (1000 mg), a low dose (700 mg), or a placebo three times daily. The study assessed changes in body weight, body composition, blood pressure, and blood biochemistry.
Factors Influencing the Effectiveness of WKBE
Several factors can influence the effectiveness of WKBE, including the specific formulation used, the dosage, the duration of supplementation, and individual characteristics. Different WKBE products may vary in their α-amylase inhibitory activity and bioavailability. The optimal dosage and duration of supplementation may also vary depending on individual factors such as body weight, diet, and activity level.
Safety and Potential Side Effects
WKBE is generally considered safe for consumption, with few reported side effects. Some individuals may experience mild gastrointestinal symptoms such as bloating, gas, or diarrhea, particularly at higher doses. These symptoms are usually temporary and can be minimized by starting with a low dose and gradually increasing it over time.
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