Fish Oil Boosts Exercise-Related Muscle Growth in Older Women

Fish oil Omega-3 may help older women avoid loss of muscle mass, strength, and function by enhancing exercise-induced muscle growth. Unfortunately, men don’t seem to gain this benefit from supplementation, though positive muscle effects are still observed in them.

Back in 2012, Stuart Gray, then a researcher at the University of Aberdeen (UK), announced at the British Science Festival the first study monitoring changes in muscle function and mass in older adults combining exercise with fish oil rich in Omega-3.

Since then, various studies have explored these fats’ benefits for muscles, suggesting that improving strength and function doesn’t always require increasing muscle mass, that effects on muscle mass may be sex-specific, and that Omega-3 are valuable allies against sarcopenia—a common and undesired condition during aging.

Protecting muscles from aging

The human body contains a large amount of skeletal muscle, which not only allows movement but is also important for overall health throughout life.

Unfortunately, during natural aging, muscle size decreases by about 0.5 to 2% per year, contributing to sarcopenia—loss of muscle mass and strength that can significantly reduce quality of life and lead to loss of independence in older age.

Exercise can help combat muscle loss, but its effectiveness decreases with age; alternative methods to protect muscles could help overcome this challenge.

Combined action of exercise and Omega-3

Both a preliminary study from the University of Aberdeen and research published in the American Journal of Clinical Nutrition by experts at the Federal University of Paraná (Brazil) suggested that in older women, exercise benefits were greater when fish oil rich in Omega-3 was taken during training.

Omega-3 fatty acids are essential nutrients, playing both a structural role (as components of cell structures, tissues, and organs) and providing health benefits such as reducing inflammation and protecting the cardiovascular system by regulating triglyceride levels.

But Omega-3s do more than support heart health: many other organs and tissues—including the nervous system, joints, and muscles—may benefit from increased intake.

Gray and colleagues focused on possible muscle benefits from these nutrients, aiming to help develop new treatments to fight sarcopenia.

Not just women

Until then mostly studied in women, the analyses were extended to men. Gray’s announced research involved men and women over 65 years old in an 18-week training program; only half received fish oil, the others a placebo.

Gray expected benefits from several mechanisms, primarily the anti-inflammatory action of Omega-3s in fish oil. In older age, inflammation increases, interfering with muscles’ ability to grow in size and strength.

“The anti-inflammatory properties of fish oil could reduce this inflammation and thus inhibit this interference,” explained Gray, adding that “Omega-3s from fish oil may also help make muscles more flexible and increase levels of proteins that promote muscle growth.”

Other authors highlighted that increased muscle protein synthesis might result from improved nutrient flow to muscles.

What effect on muscle mass?

Over subsequent years, Gray—now Professor of Muscle and Metabolic Health at the University of Glasgow (UK)—published several scientific papers on fish oil benefits for muscles.

In 2018, writing in Current Opinion in Clinical Nutrition and Metabolic Care with Bettina Mittendorfer from the University of Washington School of Medicine (St. Louis, USA), he emphasized that “results from recent studies show that in sedentary older adults, supplementation with fish oil Omega-3 polyunsaturated fatty acids stimulates muscle protein synthesis and improves muscle mass and function, and enhances muscle strength gains from resistance training.”

In 2024, a literature review published in the same journal by Gray and coauthors reported that “systematic reviews and meta-analyses of randomized controlled trials show small but clinically relevant effects of oral polyunsaturated Omega-3 fatty acid intake on strength, with variable results on changes in muscle mass and physical function.”

That same year, experts from Hosei University in Tokyo (Japan) summarized studies pairing resistance training with Omega-3 supplementation. “The meta-analysis results revealed that Omega-3 supplementation combined with resistance training significantly improved muscle strength compared to controls,” they said, but “no significant effects on muscle mass were observed.”

Omega-3 and muscles: possible women-specific benefits

Notably, the results of the study announced by Gray at the British Science Festival and published in 2017 in the American Journal of Clinical Nutrition point to possible muscle mass benefits specific to women.

Data showed increases in muscle mass and function only in women, while another well-known Omega-3 benefit (triglyceride reduction) was independent of sex.

“After resistance training,” Gray and collaborators explained, “long-chain polyunsaturated Omega-3 fatty acid supplementation (those in fish oil) increases muscle function and quality gains in older women but not in older men.”

Moreover, scientific literature suggests more than 2 grams of Omega-3 daily may be needed to increase muscle mass, and that these fats can improve muscle strength and function even without increasing muscle size.

In summary, fish oil Omega-3 may provide muscle benefits independent of muscle mass increase, but with an adequate supplementation protocol—at least 2 grams daily—muscle mass could also increase, especially in women.

Considering all results together, heterogeneity of existing studies, with differing protocols and mixed-sex participants, may mask dose-dependent and sex-specific benefits.

Further research will help confirm these findings and clarify the exact mechanisms by which Omega-3 might promote muscle mass gains.

References:

Da Boit M, Sibson R, Sivasubramaniam S, Meakin JR, Greig CA, Aspden RM, Thies F, Jeromson S, Hamilton DL, Speakman JR, Hambly C, Mangoni AA, Preston T, Gray SR. Sex differences in the effect of fish-oil supplementation on the adaptive response to resistance exercise training in older people: a randomized controlled trial. Am J Clin Nutr. 2017 Jan;105(1):151-158. doi: 10.3945/ajcn.116.140780

Gray SR, Mittendorfer B. Fish oil-derived n-3 polyunsaturated fatty acids for the prevention and treatment of sarcopenia. Curr Opin Clin Nutr Metab Care. 2018 Mar;21(2):104-109. doi: 10.1097/MCO.0000000000000441

Huang YH, Chiu WC, Hsu YP, Lo YL, Wang YH. Effects of Omega-3 Fatty Acids on Muscle Mass, Muscle Strength and Muscle Performance among the Elderly: A Meta-Analysis. Nutrients. 2020 Dec 4;12(12):3739. doi: 10.3390/nu12123739

Phillips N, Gray SR, Combet E, Witard OC. Long-chain n -3 polyunsaturated fatty acids for the management of age- and disease-related declines in skeletal muscle mass, strength and physical function. Curr Opin Clin Nutr Metab Care. 2024 Mar 1;27(2):98-105. doi: 10.1097/MCO.0000000000000986

Timraz M, Binmahfoz A, Quinn TJ, Combet E, Gray SR. The Effect of Long Chain n-3 Fatty Acid Supplementation on Muscle Strength in Older Adults: A Systematic Review and Meta-Analysis. Nutrients. 2023 Aug 14;15(16):3579. doi: 10.3390/nu15163579

Uchida Y, Tsuji K, Ochi E. Effects of Omega-3 fatty acids supplementation and resistance training on skeletal muscle. Clin Nutr ESPEN. 2024 Jun;61:189-196. doi: 10.1016/j.clnesp.2024.03.019

University of Aberdeen. Could fish oil be key in protecting the elderly against muscle deterioration? 05 September 2012. Accessed 28/04/25