ACUTE FUNCTIONAL IRON-DEFICIENCY IN OBESE SUBJECTS DURING A VERY-LOW-ENERGY ALL-PROTEIN DIET

We examined whether a very-low-energy all-protein diet (VLED) would pr oduce detectable changes in iron as well as in other trace elements. T wenty-five obese patients consumed for 2 wk a VLED containing 70 g pro tein after a I-wk period during which total daily energy intake was pr ogressively reduced to 1.26 MJ. Serum iron fell sharply by approximate to 50% (P < 0.0001), and despite a small decrease in total-iron-bindi ng capacity, transferrin saturation decreased from 30 +/- 11% to 18 +/ - 5% (P < 0.0001). Serum ferritin did not change significantly but ser um soluble transferrin receptor (sTfR), an indicator of iron deficienc y, increased progressively from 4630 +/- 1110 to 6070 +/- 1390 mu g/L (P < 0.0001). Changes in sTfR correlated inversely with prior changes in serum iron. Changes in iron metabolism did not translate into chang es in erythropoiesis or red cell indexes, but the white blood cell cou nt decreased from 7.3 +/- 1.6 to 6.2 +/- 1.9 x 10(9)/L (P < 0.002). Th ere was no evidence of deficiency for the other trace elements and min erals tested. Daily supplementation with 200 mg Fe in 18 other subject s only partially corrected these observations despite some increase in iron stores. These results indicate that during a 2-wk VLED serum iro n is significantly depressed, inducing functional tissue iron deficien cy too short in duration to produce alterations in red blood cell inde xes. These changes are not mediated by absolute iron deficiency, infla mmation, or protein malnutrition but could be related to alterations i n the iron storage and release behavior of the reticuloendothelial cel l during energy deprivation alone.