Researchers studied 296 obese children and 138 healthy children to see if being metabolically healthy (having good blood sugar, cholesterol, and blood pressure levels) protected against vitamin B12 deficiency. They found that obese children—even those who were metabolically healthy—had much lower B12 levels than healthy-weight children. About one-third of obese kids had B12 insufficiency compared to only one-sixth of healthy children. This suggests that extra body weight itself may affect B12 levels, regardless of other health markers. The findings highlight that doctors should regularly check B12 levels in obese children.

The Quick Take

  • What they studied: Whether obese children who are otherwise metabolically healthy (good blood sugar, cholesterol, and blood pressure) are protected from vitamin B12 deficiency, and how B12 levels relate to different health markers.
  • Who participated: 296 obese children with an average age of 11 years, plus 138 healthy-weight children of similar ages. The obese children were divided into two groups: those with metabolic problems (54%) and those without (46%).
  • Key finding: Obese children had significantly lower B12 levels than healthy-weight children, regardless of whether they had other metabolic problems. About 34% of obese kids had low B12 compared to 16% of healthy-weight kids. Even the ‘metabolically healthy’ obese children had B12 levels about 28% lower than healthy controls.
  • What it means for you: If your child is obese, they should have their B12 levels checked regularly, even if their blood sugar, cholesterol, and blood pressure are normal. Extra body weight itself may affect B12 absorption or storage. Talk to your doctor about whether B12 testing or supplementation is appropriate.

The Research Details

This was a cross-sectional study comparing three groups of children: obese children with metabolic problems, obese children without metabolic problems, and healthy-weight children. The researchers measured vitamin B12 levels in blood samples and checked various health markers like blood sugar, cholesterol, blood pressure, and liver function. They used statistical analysis to find connections between B12 levels and these health markers.

The obese children were classified based on whether they had any of these metabolic problems: high blood sugar (100 mg/dL or higher), high triglycerides (a type of fat in blood), low HDL cholesterol (the ‘good’ cholesterol), or high blood pressure. Children with none of these problems were considered ‘metabolically healthy obese,’ while those with one or more were ‘metabolically unhealthy obese.’

Vitamin B12 was categorized into three levels: deficient (below 200 pg/mL), insufficient (200-300 pg/mL), and sufficient (above 300 pg/mL). The researchers then looked for patterns between B12 levels and various health measurements.

This research approach is important because it challenges a common assumption: that if an obese child has normal blood sugar, cholesterol, and blood pressure, they’re essentially healthy. By comparing B12 levels across all three groups, the study shows that obesity itself—independent of these other health markers—may affect nutrient absorption. This suggests doctors shouldn’t assume obese children are fine just because their basic metabolic tests look good.

This study has several strengths: it included a reasonable sample size (434 children), used age- and sex-matched controls for fair comparison, and measured multiple health markers. However, it’s a snapshot study (cross-sectional), meaning it shows associations at one point in time but can’t prove that obesity causes B12 deficiency. The study was published in Scientific Reports, a reputable peer-reviewed journal. The main limitation is that the study can’t explain exactly why obese children have lower B12—it only shows the connection exists.

What the Results Show

The most striking finding was that obese children had substantially lower B12 levels than healthy-weight children. The metabolically healthy obese group had an average B12 level of 282 pg/mL, compared to 389 pg/mL in healthy controls—a difference of about 27%. Even more concerning, 34% of obese children had insufficient B12 levels (below 300 pg/mL) compared to only 16% of healthy children.

Surprisingly, the two groups of obese children (metabolically healthy and unhealthy) had nearly identical B12 levels. This was the key finding: being metabolically healthy didn’t protect obese children from low B12. The researchers found that for every increase in body mass index (BMI), the risk of B12 insufficiency increased by 4.3 times. This suggests that extra body weight itself is the main factor affecting B12 levels, not the presence or absence of other metabolic problems.

The study also found connections between B12 levels and several other health markers. Children with lower B12 tended to have higher triglycerides (blood fats), lower HDL cholesterol, and higher uric acid levels. There was also a connection with thyroid hormone levels. These associations suggest that B12 deficiency may be linked to broader metabolic dysfunction in obese children.

The researchers found that vitamin B12 deficiency was associated with several other health problems in obese children. Children with lower B12 had higher liver enzyme levels (AST), suggesting possible liver stress. The ratio of triglycerides to HDL cholesterol—a marker of metabolic health—was also connected to B12 levels. These findings suggest that B12 deficiency doesn’t occur in isolation but is part of a broader pattern of metabolic changes in obese children.

This study adds important new information to existing research. Previous studies have shown that obesity is associated with various nutrient deficiencies, but this is one of the first to specifically examine whether being metabolically healthy protects against these deficiencies. The finding that it doesn’t contradicts the assumption that ‘metabolically healthy obesity’ is truly benign. It aligns with growing evidence that excess body weight itself—regardless of traditional health markers—may interfere with nutrient absorption and metabolism.

This study has several important limitations. First, it’s a snapshot in time, so we can’t prove that obesity causes B12 deficiency—only that they’re connected. Second, the study doesn’t explain the mechanism: why does obesity lead to lower B12? It could be due to poor absorption in the gut, changes in how the body stores B12, dietary differences, or other factors not measured here. Third, the study only looked at children in one location, so results might differ in other populations. Finally, the study didn’t measure actual B12 deficiency symptoms or long-term health outcomes, only blood levels.

The Bottom Line

Based on this research, doctors should consider checking B12 levels in all obese children, not just those with metabolic problems. If B12 levels are low, supplementation may be recommended. However, this is preliminary evidence, and individual decisions should be made with a healthcare provider. The confidence level is moderate—the study shows a clear association but doesn’t prove causation. Parents of obese children should discuss B12 screening with their pediatrician.

This research is most relevant for parents of obese children, pediatricians, and healthcare providers treating childhood obesity. It’s also important for children themselves to understand. This doesn’t apply to healthy-weight children, who showed normal B12 levels. However, anyone concerned about B12 deficiency should consult their doctor rather than self-diagnosing based on this study.

If a child is found to have low B12 and starts supplementation, improvements in energy and symptoms might take weeks to months. However, this study doesn’t provide information about how quickly B12 levels normalize with treatment or how quickly symptoms improve. Individual responses vary, and a doctor should monitor progress.

Want to Apply This Research?

  • Track B12 supplementation (if prescribed) by logging daily doses and any symptoms like fatigue, weakness, or difficulty concentrating. Record the date of B12 blood tests and results to monitor whether levels are improving over time.
  • If your child is obese and has low B12, the app can help track: (1) B12 supplement adherence with daily reminders, (2) energy levels and symptoms on a simple scale, (3) appointment reminders for follow-up blood tests, and (4) dietary sources of B12 (meat, fish, eggs, dairy) to complement supplementation.
  • Set up quarterly reminders for B12 blood tests to monitor whether supplementation is working. Track energy levels, mood, and concentration weekly using a simple rating scale. Create a log of B12 supplement doses taken to ensure consistency. Share results with healthcare provider through the app’s health data export feature.

This research shows an association between obesity and low B12 levels in children but does not prove that obesity directly causes B12 deficiency. This information is for educational purposes only and should not replace professional medical advice. If you’re concerned about your child’s B12 levels or obesity, consult with a pediatrician or registered dietitian. Do not start B12 supplementation without medical guidance, as appropriate dosing depends on individual factors. This study was conducted in a specific population and results may not apply to all children. Always discuss screening and treatment options with your child’s healthcare provider.