Eating lots of omega-3 fatty acids, like those found in fish oil, may help your body hold onto muscle when you're eating fewer calories, like during a diet.

We analyzed the available evidence on whether omega-3 fatty acids help preserve muscle during dieting, and what we’ve found so far leans toward a possible benefit. Two assertions support the idea that consuming higher amounts of omega-3s — like those in fish oil — may help your body hold onto muscle when you’re eating fewer calories [1]. No studies or claims in our review contradicted this. The evidence we’ve reviewed is limited, with only two assertions included, and neither comes from a controlled human trial we can fully evaluate. That means we can’t say how strong this effect might be, or if it works the same for everyone. Omega-3s are fats found in fatty fish, flaxseeds, and supplements, and they’re known to play a role in reducing inflammation and supporting cell function. The idea that they might help protect muscle during calorie restriction is based on how they interact with muscle metabolism, but we don’t have enough data to know how much you’d need to eat, or how long it would take to see any effect. Because the evidence is so thin, we can’t say this works reliably or for all people. But since omega-3s are generally safe and part of a healthy diet, getting them from food — like salmon, sardines, or walnuts — might be a simple step to consider while dieting, even if the muscle-preserving effect isn’t confirmed. What we’ve found so far doesn’t prove anything, but it also doesn’t rule it out. More research is needed.