Due to the increase in the prevalence of obesity, the consumption of dietary supplements promoting weight loss has increased in the last few years. Many dietary supplements are available on the market, such as L-carnitine, glucomanan, chitosan, and Hoodia gordonii. The safety and clinical effectiveness of most of these supplements have not been assessed by high-quality trials. The scientific evidence of their benefit remains weak. The risk of adverse effects and drug interactions, most often unknown to patients, exists and must be carefully considered before initiating supplementation, in consultation with a physician, in the same way as other aspects of the treatment of obese patients.