## 5 Effects of Micronutrient Supplementation on Weight Management and Metabolic Health in Obesity  
The micronutrient supplementation in certain cases of human obesity is necessary. Some patients are forced to eliminate particular food products due to allergies or other conditions like [PERSON]'s disease (exclusion of milk and vegetables) that may induce nutritional deficiencies (Ca and vitamins C, E, and K) [45]. In addition, increased micronutrient losses through the gastrointestinal tract are typical after bariatric surgery [46; 47]. Multivitamin supplements are also recommended to women with excess weight who are pregnant to reduce the risk of preterm births and preeclampsia [48; 49] as well as to improve birth outcomes, in particular, to reduce the odds of low birth weight [50].  
On the other hand, obesity and associated metabolic dysfunctions are conditions where micronutrient supplementation becomes increasingly appreciated [51; 52; 53; 54].  
In addition to micronutrients that are deficient in people with obesity (see Table 1), the effects of supplementation on weight loss, as well as glucose and lipid homeostasis, were intensively studied for vitamin E and Cr.  
Vitamin E deficiency was reported not to occur in people with obesity [3]. However, excess weight, insulin resistance, and dyslipidemia showed reverse association with blood levels of vitamin E [6], and the number of studies on the effect of vitamin E supplementation on metabolic disorders was sufficient to enable meta-analyses [55; 56; 57]. Similarly, numerous clinical trials and meta-analyses looked at the effects of Cr supplementation [58; 59; 60]. This mineral plays an important role in the metabolism of all macronutrients [61] and has been applied in commercial weight loss supplementation for years.  
On the other hand, data on the effects of Fe supplementation on body weight, glucose, and lipid homeostasis in humans are very limited. In excess, Fe promotes the formation of reactive oxygen species and consequent DNA damage and lipid peroxidation, which contribute to the development of type 2 diabetes (T2D), cancer, and cardiovascular diseases [62]. However, longitudinal studies have shown conflicting results regarding the association of Fe intake with the abovementioned conditions [63]. Meta-analyses have indicated an increased risk of disease due to excessive consumption of heme Fe alone, which may therefore be explained by excessive consumption of high-fat meat and offal products [64; 65; 66; 67]. Some evidence linking Fe supplementation with gestational diabetes mellitus was published; however, studies reported ambiguous results indicating positive or no associations [68; 69]. On the other hand, animal studies have shown metabolic benefits from Fe supplementation. The positive effects on glucose and lipid homeostasis in obese rodents fed a high-fat diet through the regulation of mitochondrial functions and hepatocyte effects were demonstrated [70; 71]. Furthermore, dietary excess of Fe was shown to reduce the weight gain of fattened mice by 15%, which was explained by increased lipolytic processes and impairment of lipogenesis [72].  
In Sections 5.1-5.3, an overview of the effects of vitamin and mineral supplementation on weight loss and the chosen markers of glucose and lipid homeostasis extracted from meta-analyses and RCTs is given.