Improved Magnesium Levels in Morbidly Obese Diabetic and Non-diabetic Patients After Modest Weight Loss Solveig Meyer Mikalsen 1 & Anne-Lise Bjørke-Monsen 2,3 & Jon Elling Whist 1,4 & Jan Aaseth 4,5 Received: 15 March 2018 /Accepted: 12 April 2018 # Springer Science+Business Media, LLC, part of Springer Nature 2018 Abstract Serum magnesium (Mg) is reported to be reduced in individuals with obesity, hypertension, and diabetes mellitus and has been suggested as a marker for metabolic syndrome. We have studied changes in serum Mg concentrations in a group of obese patients (n = 92) with and without diabetes mellitus after weight loss induced by dieting and bariatric surgery. At inclusion, 11% (10/92) of the population had severe Mg deficiency (< 0.75 mmol/L) and median serum Mg was lower in diabetic (n = 20) compared to non-diabetic (n = 72) patients (p = 0.002). A weight loss of 10 kg after 8 weeks of lifestyle interventions was accompanied by increased serum Mg of about 5% in both diabetic and non-diabetic patients. Serum Mg remained stable thereafter in the non- diabetic patients, while it continued to increase in the diabetic patients after bariatric surgery. Six months after bariatric surgery, there was no significant difference in serum Mg concentration between the groups (p = 0.08). The optimal range of circulating Mg concentration is not known, but as even small increments in serum Mg are reported to lower the risk of cardiovascular and ischemic heart disease, our results are interesting in a public health perspective. Keywords Bariatric surgery . Diabetes mellitus . Magnesium . Metabolic syndrome . Obesity . Weight loss Introduction Obesity induces a variety of physiological changes, predispos- ing the individual to comorbidities like type 2 diabetes, hyper- tension, dyslipidemia, and coronary heart disease [1]. This is particularly alarming, given the fact that obesity prevalence is increasing worldwide [2]. Weight loss is associated with im- provement in metabolic function [3] and can be achieved by lifestyle interventions, dieting, and physical exercise [4]; how- ever, most individuals fail to maintain the weight loss and return to their initial weight [5]. Alternatively, morbidly obese patients may be referred to bariatric surgery [6], which is as- sociated with long-term weight loss and reduced prevalence of obesity-related comorbidities [7]. Serum magnesium (Mg) is reported to be reduced in indi- viduals with obesity [8], diabetes, and hypertension [9] and has been suggested as a marker and possible pathogenic factor in the cascade of signs and symptoms characterizing metabol- ic syndrome [8, 10]. Increased serum Mg concentrations have been reported after bariatric surgery-induced weight loss [11]. Mg, the second most abundant intracellular cation in the body, is known to be an essential cofactor in more than 300 enzy- matic reactions. The electrolyte is taken up in the intestine, stored in the bone, and excreted by the kidneys. Studies have suggested a role for parathyroid hormone (PTH) and 1,25-dihydroxyvitamin D (1,25(OH) 2 D) for regulating Mg absorption [12], but Mg homeostasis is still not well under- stood. Mg is vital for activation of the insulin receptor β-subunit, and patients with type 2 diabetes are reported to have lower serum Mg concentrations compared to controls [13]. Additionally, Mg supplementation is considered to have a beneficial effect on insulin resistance [14]. We have studied changes in serum Mg concentrations in a group of patients with a BMI ≥ 35, who underwent lifestyle interventions followed by Roux-en-Y gastric bypass (RYGB) during a period of 14 months. The purpose was to study * Solveig Meyer Mikalsen solveig.meyer.mikalsen@sykehuset-innlandet.no 1 Laboratory of Medical Biochemistry, Innlandet Hospital Trust, Lillehammer, Norway 2 Laboratory of Clinical Biochemistry, Haukeland University Hospital, 5021 Bergen, Norway 3 Department of Clinical Science, University of Bergen, Bergen, Norway 4 Department of Research, Innlandet Hospital Trust, Brumunddal, Norway 5 Inland Norway University of Applied Sciences, Elverum, Norway Biological Trace Element Research https://doi.org/10.1007/s12011-018-1349-3