Evidence check: tTG IgA in the context of weight loss

tTG IgA is a well-established serological marker for celiac disease, an autoimmune condition that can cause weight loss due to malabsorption. However, in the context of general weight loss (e.g., through dieting), the test is not indicated unless specific symptoms or risk factors for celiac disease are present. The evidence for using tTG IgA to guide weight loss is weak: it is a diagnostic test for a specific disease, not a biomarker for diet success. False positives (e.g., in other autoimmune diseases) are possible. Guidelines recommend targeted screening only when celiac is suspected. For general weight loss, no validated genetic or serological tests predict personalized diet outcomes – this is rejected by RCTs (e.g., POINTS trial, PMID 37813841) and professional societies (Academy of Nutrition, AHA). Therefore, tTG IgA in the context of weight loss without celiac suspicion is not evidence-based.