Obesity is a chronic condition linked to numerous health risks and affects more than one billion people worldwide. While pharmacological treatments such as incretin-based therapies are available, they may have side effects, are not suitable for all patients, and adherence can be limited. Dietary supplements that influence appetite and satiety may represent an alternative or complementary approach. This study will evaluate whether a dietary supplement containing plant extracts stimulates the intestinal incretin response. The primary focus is the effect on glucagon-like peptide-1 (GLP-1) secretion. Secondary outcomes include dipeptidyl peptidase-4 (DPP-4), gastric inhibitory peptide (GIP), and insulin, as well as measures of appetite, satiety, food intake, and anthropometrics. The trial is designed as a 12-week, double-blind, randomized, placebo-controlled parallel-group study in adults with overweight or obesity (BMI 25-40, age 18-50). Participants will receive either the dietary supplement or placebo. Blood samples will be collected at baseline and after 12 weeks, both fasting and following capsule intake and a standardized liquid meal. Anthropometric measurements and visual analog scales (VAS) for hunger and satiety will also be assessed.
Obesity is a chronic disease associated with a wide range of adverse health outcomes, including type 2 diabetes mellitus, coronary heart disease, and other metabolic disorders. The global rise in obesity is driven in part by sedentary lifestyles and the widespread availability of calorie-dense foods. According to the World Health Organization, over one billion people worldwide are affected by obesity (BMI ≥ 30 kg/m²), with even more classified as overweight (BMI ≥ 25 kg/m²). This trend poses significant challenges not only to individual health but also to public health systems due to the high costs of treating obesity-related complications. Lifestyle modification remains the cornerstone of effective weight management. For individuals with overweight but without comorbidities, the primary goal is to prevent further weight gain through increased physical activity and dietary adjustments. Evidence suggests that even modest weight loss of 5-10% can lead to clinically meaningful improvements in cardiovascular risk factors. In this context, dietary supplements that support appetite regulation and satiety enhancement are of growing interest. Several plant extracts-including bitter melon, yerba mate, green tea, turmeric, and others-have shown potential to stimulate the secretion of glucagon-like peptide-1 (GLP-1), a gut hormone involved in satiety signaling, appetite suppression, and insulin secretion. GLP-1 is secreted by intestinal L-cells in response to food intake and acts via GLP-1 receptors. However, native GLP-1 has a short half-life of approximately two minutes due to rapid degradation by the enzyme dipeptidyl peptidase-4 (DPP-4). Therefore, strategies that stimulate GLP-1 secretion or inhibit DPP-4 activity may enhance satiety and support weight control. While promising, current evidence is largely limited to in vitro and animal studies, and human data are lacking. This randomized, double-blind, placebo-controlled clinical trial aims to investigate the effects of a commercially available dietary supplement (FitLine TopShape) on GLP-1 secretion and related metabolic parameters. The supplement contains extracts from purslane, bitter melon, dandelion, mulberry, yerba mate, and green coffee beans. Preliminary user data from an observational study (n=40) suggest that daily intake of the supplement may increase satiety and promote weight loss (mean reduction: -1.32 kg over four weeks; unpublished). In vitro assays indicate that the bioactive compounds may reduce DPP-4 activity and increase GLP-1 secretion (unpublished). The primary objective of this study is to assess the effect of the supplement on GLP-1 secretion. Secondary outcomes include changes in DPP-4 activity, gastric inhibitory peptide (GIP), insulin, and C-peptide levels. Subjective measures of satiety, appetite, and food intake will be collected via validated questionnaires. Anthropometric data (weight, height, waist and hip circumference) will be recorded at baseline and after 12 weeks of intervention. Participants (BMI 25-40 kg/m², age 18-50 years) will be randomized 1:1 to receive either the dietary supplement or placebo for 12 weeks. Blood samples will be collected in fasting state and at multiple time points post-ingestion of the capsule and a standardized liquid meal. The study will evaluate both acute hormonal responses and long-term effects on weight control.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
QUADRUPLE
Enrollment
40
Capsule containing a blend of plant extracts, administered twice daily three capsules (total six capsules), 30-60 minutes before main meals, for 12 weeks.
Matching capsule without active plant extracts, administered twice daily three capsules (in total six), 30-60 minutes before main meals, for 12 weeks.
Salzburger Universitätsklinikum
Salzburg, Salzburg, Austria
RECRUITINGGLP-1 secretion
Taking the dietary supplement over a period of 12 weeks changes GLP-1 secretion (area under the curve (AUC) over 60 minutes) in overweight or obese subjects\* compared to the start of the study (AUC over 60 minutes).
Time frame: 12 weeks
Intervention vs. Placebo
Taking the dietary supplement over a period of 12 weeks changes GLP-1, DPP-4, GIP, and insulin secretion (AUC over 60 min) in overweight or obese subjects\* compared to taking a placebo (AUC over 60 min).
Time frame: 12 weeks
Liquid Meal
Taking the dietary supplement over a period of 12 weeks changes GLP-1, DPP-4, GIP, and insulin secretion (AUC over 60 min) in overweight or obese subjects\* after consuming a standardised liquid meal compared to intake at the start of the study (AUC over 60 min).
Time frame: 12 weeks
Liquid Meal: Intervention vs. Placebo
Taking the dietary supplement over a period of 12 weeks changes GLP-1, DPP-4, GIP, and insulin secretion (AUC over 60 min) in overweight or obese subjects\* after consuming a standardised liquid meal compared to taking a placebo (AUC over 60 min).
Time frame: 12 weeks
Body weight
Taking the dietary supplement over a period of 12 weeks leads to changes in body weight (kg).
Time frame: 12 weeks
Body mass index (BMI) in kg/m²
BMI in kg/m² will be determined using weight (kg) and height (m). Taking the dietary supplement over a period of 12 weeks leads to changes in BMI.
Time frame: 12 weeks
Abdominal Circumference
Taking the dietary supplement over a period of 12 weeks leads to changes in the abdominal circumference (cm).
Time frame: 12 weeks
Waist to Hip Ratio
Taking the dietary supplement leads to changes in the waist-hip ratio (cm waist/cm hip = WHR).
Time frame: 12 weeks
Changes in Control of Eating Questionnaire (CoEQ)
Participants report on their control of eating by answering the Control of Eating Questionnaire (CoEQ) with 19 questions. Rating on a horizontal, non-calibrated line of 10 cm, ranging from very low (0) to very high (10).
Time frame: 12 weeks
Visual analog scale (VAS) to assess hunger
Visual analog scale (VAS) to assess hunger on a horizontal, non-calibrated line of 10 cm, ranging from not hungry at all (0) to very hungry (10)
Time frame: 12 weeks
Visual analog scale (VAS) to assess satiation
Visual analog scale (VAS) to assess satiation (process that leads to the termination of eating) on a horizontal, non-calibrated line of 10 cm, ranging from completely empty (0) to cannot eat another bite (10)
Time frame: 12 weeks
Visual analog scale (VAS) to assess desire to eat
Visual analog scale to assess desire to eat on a horizontal, non-calibrated line of 10 cm, ranging from very low (0) to very strong (10)
Time frame: 12 weeks
Visual analog scale (VAS) to assess the amount that can be eaten right now
Visual analog scale to assess the amount that can be eaten right now on a horizontal, non-calibrated line of 10 cm, ranging from not at all (0) to a large amount (10)
Time frame: 12 weeks
Visual analog scale (VAS) to assess satiety
Visual analog scale to assess satiety (feeling of fullness that persists after eating suppressing further energy intake) on a horizontal, non-calibrated line of 10 cm, ranging from not full at all (0) to totally full (10)
Time frame: 12 weeks
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