Micronutrient deficiencies are usually associated with undernutrition. Yet, paradoxically, people living with obesity often present with inadequate levels of essential vitamins and minerals. A pilot study by Damms-Machado and colleagues (2012) takes a closer look at this hidden burden, asking two important questions: 

Baseline: Calories High, Micronutrients Low 

Before any intervention, the 104 participants with obesity (average BMI ~41 kg/m²) reported diets that were rich in calories but poor in micronutrients. Compared with a representative German reference population, both men and women with obesity had significantly lower intakes of key nutrients. More than three-quarters consumed insufficient retinol, β-carotene, vitamin D, folate, iron, and iodine, and over half were below recommendations for vitamin E, vitamin C, and calcium. 

This inadequate intake was mirrored in biological markers. At baseline, deficiencies were seen in serum for 25-hydroxyvitamin D, vitamin C, selenium and iron. These findings confirm that micronutrient shortfalls are already common in obesity, even before weight-loss treatment begins. 

The Formula Diet Experiment: 100% RDI, but Still Not Enough 

A subgroup of 32 participants followed a three-month, 800 kcal/day low-calorie diet (LCD) based entirely on a standardized formula providing vitamins and minerals at levels meeting or exceeding the RDI for healthy adults. On average, participants lost about 16% of their body weight during this phase, a clinically meaningful reduction. 

Surprisingly, the diet did not correct pre-existing deficiencies. In fact, some nutrient levels worsened: after three months, more patients showed low levels of vitamin C, selenium, zinc, iron, and calcium deficiency became more prevalent (from 0% to 53.8%). Serum vitamin D levels did improve, likely reflecting mobilization of vitamin D from fat stores during weight loss, but iron and calcium levels decreased, and antioxidant markers like vitamin C dropped further. 

Why Does This Happen? 

The study suggests several mechanisms: 

What the Authors Concluded 

Damms-Machado and colleagues emphasize that micronutrient deficiency in obesity is not corrected by a protein-rich, RDI-covering formula diet. Instead, deficiencies remain or worsen during intensive weight loss, despite intakes that formally meet nutritional guidelines .  

What This Means for Clinical Practice 

For healthcare professionals, the implications are clear: the “standard” RDI, developed for healthy, normal-weight populations, may not be sufficient for patients with obesity, especially during periods of rapid weight reduction. This highlights the importance of individualized supplementation strategies that go beyond generic RDI levels. 

Key Takeaways

• Baseline risk is high: Many people with obesity already have deficiencies in vitamin D, C, iron and selenium before any weight-loss intervention. 

• Standard RDI is not enough: A low-calorie formula diet designed to meet 100% of RDI did not correct deficiencies and, in some cases (vitamin C, iron, zinc, selenium and calcium), deficiencies worsened. Vitamin D deficiencies persisted. 

• Consider increased needs: Rapid weight loss and metabolic alterations may elevate micronutrient requirements, especially for fat-soluble vitamins and antioxidants. 

• Monitor closely: Routine assessment of both serum and cellular micronutrient status is recommended for obese patients, particularly during structured weight-loss programs. 

• Specialized supplementation may be necessary: Clinicians should consider higher-dose or tailored supplementation strategies to prevent deficiencies and support metabolic health in people with obesity.  

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