Which food supplements can support weight loss?

What do recent studies say on the effectiveness of food supplements for weight loss?

How many kilos can be lost on average with a food supplement?

The average weight loss attributable to a food supplement lies between -0.3 and -2 kg over several months. All these results share a common feature: they were obtained in participants who were already eating less or moving more^[13]. Food supplements for weight loss play at best a supporting role alongside a calorie deficit, never that of a miracle fat burner. A network meta-analysis published in 2023 in Pharmacological Research pooled 111 randomised clinical trials and 6,171 overweight or obese adults^[1]. Out of 18 nutraceuticals evaluated, psyllium comes top with an average loss of -3.7 kg^[1]. Next come Nigella sativa (-2.1 kg) and spirulina (-1.8 kg)^[1]. Glucomannan reaches -1.36 kg and green tea -1.25 kg, with a level of evidence rated as low in both cases^[1]. Several other ingredients show no significant effect on weight management, whatever the form of the formula (capsule, powder or drinkable solution).

Why is a statistical effect not always a useful effect in practice?

A statistically significant effect is not always a useful effect in practice. When a meta-analysis measures -0.35 kg over 12 weeks between a product and a placebo, the result is mathematically real but clinically negligible compared with a goal of several kilos. This is exactly what Asbaghi 2023 concludes on conjugated linoleic acid (CLA): 70 randomised trials, 4,159 participants, and an effect “that may not reach clinical importance”^[11]. The higher-quality studies also show no effect of CLA on fat mass or muscle mass^[11]. In plain terms: a supplement that helps you lose a few hundred grams neither transforms the silhouette nor changes the basic energy expenditure, and its nutritional effect remains insignificant on the body over the medium term.

Which supplements offer the strongest evidence in 2026?

Do glucomannan and satiety fibres have a documented effect?

Glucomannan and satiety-promoting fibres have the most tangible evidence among supplements, without being miraculous. Glucomannan is a plant fibre extracted from konjac that swells on contact with water in the stomach, prolongs the feeling of fullness and helps to reduce appetite between meals. In the Shahinfar 2023 meta-analysis, this ingredient leads to an average loss of -1.4 kg, with a level of evidence rated as low^[1]. A randomised trial published in 2024 combined glucomannan, inulin and psyllium in 112 obese adults over 180 days^[9]. Participants lost on average 4.9% of their body weight and 13% of fat mass compared with placebo^[9]. The downside: 74.6% of the active group reported at least one adverse effect, mainly digestive (flatulence and abdominal discomfort, generally mild to moderate)^[9]. The effect exists, but the digestive comfort limits long-term use.

Do green tea and caffeine really help burn fat?

Green tea and caffeine have a real but marginal effect on fat loss, only when combined with an active lifestyle. A Gholami 2024 meta-analysis compared an exercise programme with or without extract of this plant in overweight adults, across 10 randomised trials^[8]. Adding green tea, combined with regular physical activity, brings an additional “small but consistent” reduction in weight and fat mass^[8]. No effect was observed on the lipid profile (cholesterol, triglycerides)^[8]. At high doses, the EGCG of green tea may be linked to rare but documented liver damage: watch out above 800 mg per day. Without sport or physical activity to support metabolism, the thermogenic effect of caffeine or catechins remains anecdotal on the scales and on basal metabolism.

Are probiotics and berberine effective for weight loss?

Probiotics and berberine give modest results, highly dependent on context. On berberine, whose tablets are sometimes used to act on blood sugar, an Elahi Vahed 2025 meta-analysis pooled 23 randomised trials and observed -0.88 kg of weight, -0.48 point of BMI and -1.3 cm of waist circumference^[10]. No effect was detected on the waist-to-hip ratio^[10]. On probiotics, results are contradictory depending on the strain used. A systematic review of 87 trials and 6,086 adults associates certain strains with a modest reduction in weight and fat mass^[5]. The authors stress, however, that evidence of a causal link remains limited^[5]. Conversely, 13 trials on 693 patients after bariatric surgery show no effect on excess weight loss^[6]. In metabolic syndrome, probiotics and synbiotics deliver -0.79 kg and -1.04 cm of waist circumference across 24 trials^[7]. The result therefore depends on the patient’s profile and the strain.

Which supplements are disappointing or risky for weight loss?

Which popular supplements lack evidence of effectiveness?

Several very popular supplements show no significant effect in rigorous studies. Astaxanthin, an antioxidant often sold as a slimming or anti-cellulite aid by certain slimming-product brands, brought no significant reduction in BMI or weight in the Laurindo 2025 meta-analysis, which pools 9 clinical trials^[12]. No dose-response correlation was detected either^[12]. CLA (conjugated linoleic acid), long presented as the best miracle fat-burning supplement, reaches only an effect of -0.35 kg considered without clinical relevance^[11]. Products labelled “fat burner”, “fat binder”, “drainer” or “appetite suppressant” without specifying their composition or providing a clinical study reference rarely rest on solid evidence.

Which substances are banned in Switzerland for weight loss?

Three substances commonly associated with weight loss are strictly banned in Switzerland. The FSVO (Federal Food Safety and Veterinary Office) prohibits 2,4-dinitrophenol (DNP)^[4], an industrial chemical that can cause fatal poisoning, dimethylhexanamine (DMAA)^[4], and dehydroepiandrosterone (DHEA)^[4], an anabolic steroid. These substances regularly reappear in products ordered for sale on foreign websites, outside the Swiss or European pharmacy circuit, and not labelled in French, German or Italian — a major point of caution for the consumer. Red yeast rice is praised for its effects on cholesterol and sometimes on weight. It is, however, not compliant with Swiss regulations, either as a foodstuff or as a medicine, because of serious doubts about its safety^[4].

How can you integrate a food supplement into a weight-loss approach?

In which cases can a supplement really help?

A supplement can support a weight-loss approach only if it is added to a genuine calorie deficit. The French researcher Max Lafontan, a global reference on adipose tissue, is explicit: the treatment of obesity rests above all on “behavioural approaches”, that is, a balanced diet and regular physical activity^[13]. No recent meta-analysis shows a significant effect of supplements taken “alone”, without a change in healthy lifestyle or eating habits^[1]. Fibres such as glucomannan can help to better manage hunger between meals and limit snacking or extras during a diet, while green tea adds a marginal effect to physical exercise. But the FSVO points out that people who follow a varied and balanced diet do not, as a rule, need food supplements to support a healthy diet^[3]. For weight loss, expectations must remain modest — and the scales secondary to the fork and the running shoes.

When should you consult a professional rather than self-supplement?

Medical advice is essential in cases of obesity (BMI ≥ 30), chronic disease or ongoing treatment. Obesity is recognised by the WHO as a chronic disease^[2] and calls for medical management, not self-medication or advice picked up online. Several supplements interact with common medicines: St John’s wort with antidepressants and the contraceptive pill, berberine with antidiabetic drugs, fibres with the absorption of certain thyroid medicines. In pregnant or breastfeeding women, pregnancy also requires specific precautions. In obesity with comorbidities, validated and supervised pharmacological treatments (GLP-1 analogues, for example) or bariatric surgery deliver results far beyond those of any supplement. Before choosing a product, contacting a doctor or pharmacist — or a dietitian service — helps to avoid false leads, risky interactions and tolerance problems.

Frequently asked questions