Myths vs facts: FADS1 and weight loss

FADS1 encodes delta-5 desaturase, a key enzyme in polyunsaturated fatty acid (PUFA) metabolism, converting linoleic acid to arachidonic acid and alpha-linolenic acid to EPA/DHA. Common variants (e.g., rs174537) alter enzyme activity and blood PUFA levels. The myth: that FADS1 variants predict or cause weight loss. The fact: GWAS show weak, inconsistent associations with BMI or adiposity; effect sizes are tiny. FADS1 may influence inflammation and lipid profiles, but direct weight loss effects are not supported by strong human evidence. Weight loss is driven by energy balance, diet quality, and physical activity, not a single SNP. Some DTC tests overstate the link, but the science is mechanistic at best. Consumers should not base diet decisions on FADS1 results. Evidence is graded as mechanistic/GWAS with low clinical utility.