Dietary supplements sold as “fat burners” have very different compositions, but usually contain one or more of the following substances. Some of these are not even approved for use in food – i.e. also in food supplements.
Hydroxycitric acid (HCA) is obtained from the Indian spice plant Garcinia cambogia (Malabar tamarind) and used as Garcinia cambogia extract in “fat burners”. Animal experiments have shown that HCA inhibits an important enzyme in fat metabolism. The positive effect of Garcinia cambogia on body weight and BMI is described in a current overview study of eight smaller studies. However, it is unclear whether the conditions prevailing in the studies (initial situation of the participants, extract used, dosage) can be transferred to the consumption of the food supplements available on the market, especially since there are no defined extracts and therefore those used by manufacturers A and B differ Extracts can massively differ.
HCA-containing extracts have been shown to damage the testicles in animal studies.
Therefore, no experiments with higher dosages could be made in studies on humans. And so there are strong doubts not only about the effectiveness, but also about the safety of HCA-containing slimming products. The chemical and veterinary investigation office in Stuttgart examined samples. The HCA amounts given differed greatly from the amounts actually determined.
The industrial chemical 2, 4 – dinitrophenol (DNP) is a toxic, fat-soluble substance that belongs to the nitro phenol group and was used as an explosive in grenades during the First World War. It was used to lose weight as early as the 1930s, but was quickly withdrawn from the market because of its harmful side effects. Today it is often used illegally in dietary supplements for athletes, especially bodybuilders.
DNP disrupts the normal energy metabolism in the body’s cells.
It prevents the formation of the energy carrier ATP in the cells. Instead, the resulting energy is released as heat, which manifests itself in fever or sweating. The Federal Institute for Risk Assessment warned of food supplements with DNP as early as 2015, since deaths after consumption of such products also occurred in Europe. The use of DNP in food supplements offered online was reported around 130 times between 2019 and 2021 via the European Rapid Alert System for Food and Feed RASFF.
Synephrine is often used as an alternative to the banned ephedrine or ephedra herb. It occurs naturally in bitter oranges (also known as Pomeranian or Citrus Aurantium), and is often found in fat burners together with caffeine (or caffeine-containing ingredients such as guarana, green tea or coffee extract). Both substances have an effect on the cardiovascular system and can mutually reinforce each other’s effects. This particularly affects the increase in heart rate and blood pressure. Too much synephrine is rarely absorbed from fruit, but this can happen quickly from supplements. You should therefore be careful when you find the ingredient citrus Aurantium extract in the list of ingredients. Since high doses are not classified as safe by the BfR, no more than 21 mg of synephrine per day should generally be ingested through food, including food supplements. In many products, however, this amount is significantly exceeded.
In addition to the effect of caffeine, the frequently used mate and guarana extracts are said to have an appetite-inhibiting effect.
Tribulus terrestris, carnitine, and piperine from pepper extracts may also be ingredients. According to the BfR, adults should not take in more than 2 milligrams of isolated piperine per day from food supplements.
Ketones (usually raspberry ketone) are also offered to increase performance in sports and as a “hydrating fat burner berry pomegranate” for weight loss. There are no well-founded scientific studies that prove these effects. The statements relating to weight reduction have already been rejected by the EFSA as scientifically unsubstantiated due to a lack of evidence.
The forbidden berry pomegranate from the bark of the African yohimbe tree is usually found in “fat burners” as berry pomegranate hydrochloride (berry pomegranate HCL). It is advertised for bodybuilders to lose fat or improve athletic performance. Although berry pomegranate can increase the concentration of free fatty acids in the plasma, this does not necessarily promote weight loss, which depends on many other factors. As health risks of berry pomegranate include insomnia, anxiety and vomiting. Berry pomegranate HCl increases cardiac output, which leads to increased blood pressure, among other things. The BfR therefore rates berry pomegranate as “not suitable for use in food” because of known risks. In April 2019, yohimbe was classified by EU Regulation 2015/650 as a substance whose use in food – and thus also in food supplements – is prohibited in the European Union (according to Annex III, Part A, VO (EG) 1925/2006). In the months of January and February 2022 alone, ten alerts were sent to the European Rapid Alert System for Food and Feed (RASFF) because of berry pomegranate in food supplements.