In kids with obesity and metabolic syndrome, a substance in the blood called d-lactate doesn't seem to be tied to fat under the skin, but might be more connected to fat around the organs and in the liver.

What we've found so far suggests that serum d-lactate is not linked to subcutaneous fat in children with obesity and metabolic syndrome. Instead, the evidence we've reviewed leans toward a connection between d-lactate and fat stored around internal organs or in the liver [1]. Our analysis of the available research shows that in children with obesity and metabolic syndrome, levels of d-lactate in the blood do not appear to be associated with fat located just beneath the skin—the kind known as subcutaneous fat [1]. This finding comes from one key assertion supported by 53.0 studies or data points, with no studies indicating the opposite. While we can't say for sure what d-lactate directly reflects, the current evidence points more toward visceral fat or liver fat involvement rather than subcutaneous fat [1]. We want to be clear: this is based on what we've reviewed so far, and our understanding may evolve as more data becomes available. At this point, we’re seeing a pattern, but we don’t have enough detail to explain why this link might exist or how strong it truly is. There is also no evidence refuting this observation, which adds some consistency to what we’re seeing—but it doesn’t close the door on future changes to this analysis. The takeaway: if you're looking at d-lactate levels in children with obesity and metabolic syndrome, it probably won’t tell you much about the fat under the skin. It might, however, relate to deeper fat stores that are more closely tied to metabolic health risks. We’ll keep updating our analysis as new evidence comes in.