When obese women take a high dose of omega-3 fish oil supplements, their blood levels of a certain inflammation marker drop while they're taking it, but go back up after they stop. However, their cells still keep the gene for that marker turned down, which means the body is handling the marker in two different ways.

We analyzed the available evidence and found that when obese women take high-dose omega-3 fish oil supplements, their blood levels of TNF-alpha—a protein linked to inflammation—tend to decrease while they’re taking the supplement. But once they stop, those blood levels rise again, returning to where they were before [1]. What we’ve found so far suggests the body responds in two different ways. While the supplement is being taken, the amount of TNF-alpha in the blood goes down. After stopping, even though the blood levels go back up, the cells still keep the gene that makes TNF-alpha less active. This means the body’s internal control over the marker hasn’t fully reset—it’s still holding onto some of the changes from the supplement, even if the visible effect in the blood fades [1]. This doesn’t mean the supplement permanently lowers inflammation. It also doesn’t mean the effect is gone entirely. The gene activity staying lower could hint at a lingering biological shift, but we don’t yet know if that has any real impact on health outcomes like weight, energy, or disease risk. We don’t have enough evidence to say whether this gene-level change is meaningful over time, or if restarting the supplement would bring blood levels down again. The data we’ve reviewed shows a pattern: benefit while taking it, return to baseline after stopping, but with a subtle cellular memory. For now, if you’re an obese woman considering high-dose omega-3s to help manage inflammation, you might see a drop in TNF-alpha while taking it—but don’t expect the effect to stick after you stop. The body may still be quietly adjusting behind the scenes, but the visible change in your blood won’t last.