How are IgG and weight loss related?

The relationship between IgG and weight loss is not clearly established in evidence-based medicine. IgG antibodies are often marketed in the context of food sensitivity testing, but their role in weight management is controversial. In celiac disease, an IgA-mediated autoimmune condition, untreated disease can cause malabsorption and weight loss – here IgA (not IgG) is the diagnostic standard. IgG tests for 'delayed food allergies' are commonly sold directly to consumers, but major allergy and gastroenterology guidelines (e.g., DGAKI, EAACI) advise against them, as IgG may simply reflect normal immune exposure to foods. Some small studies suggest that IgG-guided elimination diets can lead to short-term weight loss, but the evidence is weak, often confounded by placebo effects and dietary changes. Overall, IgG testing for weight loss is more marketing than science. For suspected celiac disease, IgA-based testing is appropriate. For general weight loss, evidence-based approaches like calorie restriction, balanced nutrition, and physical activity remain the gold standard.