The Reality Check
No supplement produces clinically meaningful weight loss on its own. The largest effects seen in meta-analyses — about 1–2 kg for berberine and protein — are modest compared to dietary and behavioral interventions (5–10 kg), let alone pharmaceutical options like GLP-1 agonists (12–17%). This guide presents the evidence honestly so you can calibrate expectations.
Evidence Summary
| Supplement | Evidence | Key Finding | Dosage |
|---|---|---|---|
| Protein (whey/other) | Strong | -1.6 kg vs controls; preserves lean mass in deficit[1] | 1.2–1.6 g/kg/day |
| Green Tea Extract | Moderate | -0.74 kg body weight; -1.04 cm WC; 59 RCTs[3] | 250–500 mg EGCG/day |
| Berberine | Moderate | -0.88 to -2.07 kg; also reduces TG and glucose[5] | 900–1,500 mg/day |
| Probiotics | Moderate | Reduces WC and visceral fat in obese; inconsistent for BW[7] | 10⁹–10¹⁰ CFU/day |
| Fiber supplements | Moderate | +14 g/day fiber = -10% energy intake, -1.9 kg/3.8 mo[9] | 10–14 g/day additional |
| Creatine | Strong (composition) | +0.82 kg lean mass, -0.28% body fat; BW increases[10] | 3–5 g/day |
| CLA | Limited | -0.44 kg fat mass; clinically insignificant in high-quality studies[11] | 3.2 g/day |
| Ashwagandha | Limited | Some evidence for stress-related weight management; insufficient for direct weight loss | 600 mg/day |
| Collagen | Insufficient | No meaningful evidence for weight loss specifically | — |
| Sea Moss | Insufficient | No clinical trials for weight loss in humans | — |
What Has Real Evidence
Protein Supplementation
The strongest evidence for any "weight loss supplement" — though it works through appetite regulation and metabolic rate, not fat-burning. A meta-analysis of 37 studies found higher protein intake reduced body weight by approximately 1.6 kg vs. controls. A separate review of 47 studies (3,218 participants) confirmed that enhanced protein preserves lean mass during caloric deficit in overweight and obese adults.[1][2] Protein from food works just as well as protein supplements.
Green Tea Extract
A 2025 GRADE-assessed dose-response meta-analysis of 59 RCTs (3,802 participants) found green tea catechins reduced body weight by 0.74 kg, BMI by 0.29, waist circumference by 1.04 cm, and body fat by 0.65%. Effects were larger in overweight/obese women (-1.23 kg body weight, -3.46 cm WC).[3][4] The active component (EGCG) works through thermogenesis and fat oxidation.
Berberine
Three meta-analyses consistently show modest weight reduction (0.88–2.07 kg) alongside improvements in metabolic markers. Berberine's value may be greatest in people with metabolic syndrome, where its combined effects on weight, glucose, triglycerides, and inflammation are clinically meaningful together. Read our full analysis →
Probiotics
Evidence is emerging but inconsistent. A 2025 meta-analysis of 8 RCTs in obese patients found significant reductions in body weight, waist circumference, and visceral fat.[7] However, a 2024 review of 11 RCTs in overweight women found WC reduction but no significant effect on body weight or BMI.[8] Multi-strain formulations and durations of 8+ weeks appear more effective.
Fiber Supplements
A meta-analysis found that an additional 14 g/day of fiber was associated with a 10% decrease in energy intake and 1.9 kg weight loss over 3.8 months in obese individuals.[9] Fiber works primarily through appetite suppression — it increases satiety, slows gastric emptying, and modulates gut hormones. Getting fiber from food (legumes, vegetables, whole grains) is equally or more effective than supplements.
Creatine (Body Composition)
Creatine is not a weight loss supplement — it increases total body weight by ~0.86 kg. However, it improves body composition by increasing lean mass (+0.82 kg) and reducing body fat percentage (-0.28 to -0.88%), especially with resistance training. For people who care more about how they look than what the scale says, this is relevant. Read our full analysis →
What Doesn't Hold Up
CLA (Conjugated Linoleic Acid)
A meta-analysis of 70 RCTs (4,159 participants) found tiny reductions: -0.35 kg body mass, -0.44 kg fat mass, -0.77% body fat. When limited to high-quality studies only, CLA failed to produce significant changes in fat mass or body fat percentage.[11] The effects are clinically insignificant.
Collagen, Sea Moss, Turmeric, B12
Despite their popularity on social media for weight loss, none of these have meaningful clinical trial evidence supporting direct weight loss effects in humans. Turmeric has some evidence for anti-inflammatory benefits, and B12 is essential for energy metabolism, but neither produces measurable weight reduction in the research.
What to Consider
- Caloric deficit is non-negotiable. No supplement bypasses thermodynamics. Even the most effective options (protein, green tea) work by modestly shifting the energy balance equation — not by "burning fat" independently.
- Metabolic context matters. Berberine and probiotics show stronger effects in people with metabolic dysfunction (insulin resistance, metabolic syndrome). If your metabolism is healthy, the incremental benefit shrinks.
- Body composition ≠ body weight. Creatine and protein both improve body composition while potentially increasing scale weight. Using body fat percentage, waist circumference, or how clothes fit may be more meaningful metrics.
- Pharmaceutical options exist. For significant obesity (BMI 30+), GLP-1 receptor agonists produce 12–17% body weight loss — an order of magnitude beyond any supplement. Discuss with your provider.
Frequently Asked Questions
What supplement has the best evidence for weight loss?
Higher protein intake has the strongest evidence, with ~1.6 kg more weight loss than controls while preserving lean mass. But this works through appetite and metabolism, not "fat burning" — and protein from food works equally well.
Does berberine help with weight loss?
Moderately. Three meta-analyses show 0.88–2.07 kg weight reduction with berberine at 900–1,500 mg/day. It also improves metabolic markers. It is not comparable to GLP-1 drugs despite social media claims. Full analysis →
Does creatine help with weight loss?
No — creatine increases total body weight. But it improves body composition: more lean mass, less body fat percentage. It's for body recomposition, not scale weight reduction. Full analysis →
References
- Higher protein intake and weight loss. 37 studies. PMID: 39002131. PubMed
- Enhanced protein preserves lean mass. 47 studies, 3,218 participants. PMID: 35871954. PubMed
- Green tea dose-response meta-analysis. 59 RCTs, 3,802 participants. 2025. PMID: 40326418. PubMed
- Green tea GRADE-assessed review. 2024. PMID: 38031409. PubMed
- Elahi Vahed I, et al. "Berberine on obesity indices." Int J Obesity. 2026. 23 articles. PubMed
- Asbaghi O, et al. "Berberine on obesity, inflammation, liver enzymes." Clin Nutr ESPEN. 2020. 12 RCTs. PubMed
- Probiotics in obese patients. 8 RCTs, 412 patients. 2025. PMID: 39984625. PubMed
- Probiotics in overweight women. 11 RCTs. 2024. PMID: 39114432. PubMed
- Fiber and energy intake/weight loss. Obese populations. PMID cited in research.
- Pashayee-Khamene F, et al. "Creatine on body composition." J Int Soc Sports Nutr. 2024. 143 RCTs. PubMed
- CLA meta-analysis. 70 RCTs, 4,159 participants. PMID: 37671495. PubMed