Obesity has become a global health concern, linked to various diseases such as type 2 diabetes, hypertension, and cardiovascular illness. While various strategies exist to manage overweight and obesity, including lifestyle changes and prescription drugs, alternative medicines, particularly natural botanicals, are gaining attention due to their effectiveness and safety. Green bean coffee (GBC), rich in nutrients and bioactive substances like chlorogenic acids (CGA), is believed to aid in weight loss. This article provides a comprehensive review of the existing research on the effects of green coffee bean extract (GBCE) on weight loss, focusing on studies utilizing at least 500 mg of CGA per day.
Understanding Obesity and Current Management Strategies
Obesity, characterized by excessive body weight, is defined by a body mass index (BMI) over 30 kg/m2, while a BMI over 25 kg/m2 indicates overweight. Several strategies are recommended for managing overweight and obesity, including dietary modifications, lifestyle changes, increased physical activity, behavior modification, and, in some cases, surgery. Prescription drugs like orlistat, lorcaserin, and liraglutide are also considered for long-term therapy. However, these drugs often come with adverse reactions, such as nausea, vomiting, and gastrointestinal discomfort. This has led to increased interest in alternative medicines, particularly natural botanicals, which are perceived as safer and more effective.
The Potential of Green Coffee Bean Extract
Green coffee beans contain potent nutrients and bioactive substances, including caffeine, caffeic acid, and chlorogenic acids (CGA). GBC is associated with reducing the risk of insulin resistance and obesity and possesses anti-inflammatory and antioxidant properties. CGA exhibits antidiabetic, anti-lipidemic, and anti-obesity properties, regulating glucose and lipid metabolism and inhibiting lipid absorption. Studies suggest that CGA and caffeic acid improve body weight, lipid metabolism, and obesity-related hormone levels.
Meta-Analysis of GBCE and Weight Loss
To evaluate the impact of GBCE containing CGA on body weight, a systematic review and meta-analysis of randomized controlled trials (RCTs) was conducted. The meta-analysis included three RCTs with 103 individuals, examining the impact of GBCE containing at least 500 mg of CGA per day on body weight. The combined findings indicated that GBCE with CGA at least 500 mg/day results in body weight reduction.
Methods Used in the Meta-Analysis
The meta-analysis followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and was documented in PROSPERO. Electronic databases, including Scopus, Embase, PubMed, and Cochrane Library, were searched up to October 13, 2022. The RCTs considered involved patients over the age of 18 and provided data for body weight as the main outcome. Studies using a dosage of chlorogenic acid less than 500 mg were excluded. Data extraction and quality assessment were conducted by multiple researchers, with disagreements resolved through discussion. The Cochrane risk-of-bias (RoB) tool version 2.0 was used to evaluate the quality of individual studies.
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Results of the Meta-Analysis
The meta-analysis revealed that GBCE supplements reduced body weight compared to a placebo. The studies showed no evidence of heterogeneity, indicating that GCBE (500 mg/day) may have decreased body weight by 1.30 kg. Begg’s and Egger’s tests did not reveal any statistically significant publication bias.
Quality of Evidence
The quality of evidence was assessed using the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) approach. While one of the included RCT studies had a high risk of bias, the intervention and outcome measures were predicted to be comparable among the included RCT trials, and heterogeneity was low.
Discussion of the Findings
The findings of the meta-analysis align with multiple comprehensive analyses of clinical studies demonstrating that GBCE supplementation can encourage weight reduction, lower obesity, fasting blood glucose levels, and improve lipid profiles. GBCE also has activity against fat accumulation. Studies suggest that green coffee bean extract administration reduces weight gain and visceral fat accumulation, potentially due to its active compounds, caffeine and CGA. Coffee bean extract is considered to reduce adipose tissue weight and attenuate body weight gain by increasing lipogenic enzyme activity and decreasing lipolytic enzyme activity.
The Role of Chlorogenic Acids
Chlorogenic acids (CGA) are polyphenols with anti-oxidant properties found in coffee beans. Clinical trials have demonstrated the various effects of CGA consumption on vascular endothelial function, blood pressure, sleep quality, and brain function. Some randomized clinical trials indicate that consuming high levels of CGA or green coffee extract that contain abundant CGA can reduce body weight and/or waist circumference (WC).
A study involving healthy, overweight men and women found that visceral fat area (VFA), total abdominal fat area (TFA), body weight, and waist circumference significantly decreased in the high-CGA coffee group compared with the control group.
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Research on Type 2 Diabetes Patients
Research has also explored the effects of green coffee extract (GCE) supplementation on cardiometabolic risk factors in patients with type 2 diabetes (T2D). A randomized, double-blind, placebo-controlled trial involving patients with T2D and overweight/obesity found that GCE supplementation led to a significant decrease in weight, BMI, systolic blood pressure, serum triglycerides, and CRP levels, and a significant increase in serum HDL levels.
Further Research and Considerations
While the existing research suggests that GBCE with CGA 500 mg/day lowers body weight, it is essential to acknowledge the limitations of the studies, such as limited sample sizes and short-term study durations. Further research is needed to fully understand the long-term effects and optimal dosages of GBCE for weight loss.
Considerations for Coffee Consumption
Coffee is consumed globally and has various beneficial effects on health. Habitual coffee consumption has been linked to a decreased risk of cardiovascular disease. However, the specific components associated with the beneficial effects of coffee consumption are still being investigated. Factors such as the form of CGA consumption (instant coffee, drip-coffee, or pre-packed coffee beverage), the source of CGA (green coffee beans or roasted coffee beans), and the roasting method can influence the bioavailability of CGA.