Fish oil is a dietary supplement derived from the tissues of fatty fish, including tuna, salmon and cod. Fish oil is a known rich source of omega-3 fatty acids, which can reduce the risk of death in people with cardiovascular disease. The National Institutes of Health indicates that fish oil can help promote weight loss. Recently, however, researchers have found that in cancer patients, fish oil can prevent weight loss and actually encourage the development of muscle mass.
Weight Gain
In 2011, researchers from the University of Alberta in Edmonton, Canada analyzed the effect of fish oil supplements on chemotherapy patients. Chemotherapy can cause patients to become malnourished, lose muscle mass and ultimately worsen quality of life and lead to a shortened lifespan. In a 10-week trial involving 16 patients on 2.2 g of fish oil supplements compared to 24 patients undergoing standard chemo care without supplementation, muscle and fat were measured periodically. Patients under standard care lost an average of 2.3 kilograms. Those on the fish oil supplement maintained their weight. Additionally, patients with the greatest gain in muscle also had the highest concentration of eicosapentaenoic acid in their blood---a type of acid from fish oil. The researchers did not analyze whether fish oil supplementation causes muscle mass gain in healthy individuals.
Muscle Mass
In 2010, a study published by the "Journal of the International Society of Sports Nutrition" aimed to determine the effects of supplemental fish oil on body composition as well as metabolic rate. A group of 44 men and women were assigned either 4 g of safflower oil or 4 g of fish oil for six weeks. By the end of the study, volunteers who had taken fish oil had a significant increase in fat-free muscle mass compared to those on safflower oil. There was also a tendency for those on fish oil to reduce fat mass. There was, however, no difference in body mass between the two groups. Data indicate that people on fish oil can gain muscle weight, but may not actually gain pounds since inch for inch, muscle mass weighs less than fat mass.
Food vs. Supplements
While most studies point to fish oil as a positive influence on weight, getting your recommended intake of omega-3 fatty acids through food can lead to weight gain. The University of Maryland Medical Center reports that omega-3 fatty acids are an essential nutrient for human health. According to the Harvard School of Public Health, it's better to get it from foods rather than from supplements since foods have other good nutrients, such as proteins and minerals. While you should aim to get at least one rich source of dietary omega-3 fatty acids a day, overdoing it doesn't improve your stores of essential nutrients, but rather can lead to weight gain.
Risks
Taking a fish oil supplement comes with risks. According to MayoClinic.com, some species of fish used to extract the oils carry a higher risk of environmental contamination, such as mercury and industrial chemicals. MedlinePlus reports that fish oil is "likely safe" for most people, including pregnant and breastfeeding women when taken in doses of 3 g or less per day. Taking more than 3 g is "possibly unsafe" and can interfere with the ability of blood to clot and increase the risk of bleeding.
References
- MedlinePlus: Fish Oil; February 2011
- MayoClinic.com: Omega-3 Fatty Acids, Fish Oil, Alpha-Linolenic Acid; April 2011
- "Journal of the International Society of Sports Nutrition"; Effects of Supplemental Fish Oil on Resting Metabolic Rate, Body Composition, and Salivary Cortisol; Eric E. Noreen; October 2010
- ScienceDaily: Fish Oil Fights Weight Loss Due to Chemotherapy; February 2011
- "Journal of the American Geriatrics Society"; Omega-3 Fatty Acid Supplementation Effects on Weight and Appetite in Patients With Alzheimer's Disease; Irving GF; March 2009
- University of Maryland Medical: Omega-3 Fatty Acids
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