Written by Team MD
20 January 2014

Fish Oil- Decreases Fat & Increases Lean Body Mass



fishoilConsuming fish or Omega-3-rich fish oil is a sure way to lose weight slowly but consistently. Fish oil makes you "look good and feel good." The key to weight loss is to lose fat one pound at a time. Small changes in weight won't give you a killer body right away. The accumulation of many small changes over time makes a huge impact. Most people won't do the work it takes to lose a lot of weight, let alone devote any effort to small, barely noticeable changes. Added up, many small changes in weight make major differences in how you look and feel. To be practical, small changes should be inexpensive, automatic, and near-effortless. Fish oil fits the bill!


The goal of bodybuilding mirrors that of every frustrated office worker, teacher, and homemaker- to drop fat and tone muscle. Daily fish oil supplements, or eating fish frequently, helps cut body fat. Even better, fish oil promotes abdominal fat loss. Gut fat is linked to heart disease, diabetes, abnormal blood fats, and high blood pressure.


A recent study published in the Journal of the International Society of Sports Nutrition investigated the effect of fish oil supplements on healthy male and female adults. The fish oil supplements contained 1,600 milligrams of EPA and 800 milligrams of DHA. After six weeks, the fish oil decreased fat and cortisol (a stress hormone) and increased muscle mass. Fish oil caused a slight increase in caloric expenditure and fat burning compared to a placebo (fake fish oil).


Consuming just two fish oil capsules with breakfast and dinner will decrease body fat and increase lean mass, which will make you look better and feel healthier. In other words, fish oil causes small but noticeable differences in making you look and feel better. The absolute differences were small. The fish oil-treated subjects lost about a pound of body fat and gained a pound of lean mass, dropping about one-half percent body fat (measured using the Bod Pod, a very cool device). The control group gained a few ounces of fat and lost a couple ounces of lean mass in comparison, gaining 0.3 percent body fat in the process.

The Cortisol Connection


Fish oil may cause fat loss by decreasing cortisol- a stress hormone linked to fat gain. The test subjects lost fat, despite no changes in the rate of calorie or fat burning. The research team discovered that the fish oil reduced cortisol, which decreased fat storage, increased the release of stored fat, and preserved metabolically active muscle tissue. The omega-3 fatty acids DHA and EPA in fish oil improved body composition by decreasing cortisol levels.


The researchers measured cortisol in saliva, which is only a rough measure of cortisol levels in blood, fat, or muscle. We need more thorough studies to find out why fish oil promotes fat loss. The bottom line is that fish oil has shown once again that it is effective for managing fat mass and body composition.


What is the take home message? Fish oil, either from Omega-3-rich fish or capsules, decrease fat mass and body weight and increasing muscle mass. This is in addition to the numerous health benefits in the brain, heart, blood vessels, and metabolism. It takes little effort to add fish oil to the diet or supplement pack, and is relatively inexpensive. Fish oil will not produce an overnight impact, and won't make you an instant winner on "The Biggest Loser" TV show. Daily fish oil supplements will eventually help you reach your goal, particularly when combined with exercise and a healthy diet.




Dangour AD, Allen E, et al. Effect of 2-y n-3 long-chain polyunsaturated fatty acid supplementation on cognitive function in older people: a randomized, double-blind, controlled trial. Am J Clin Nutr, 2010 Jun;91(6):1725-32.


Defilippis AP, Blaha MJ, et al. Omega-3 Fatty acids for cardiovascular disease prevention. Curr Treat Options Cardiovasc Med, 2010 Aug;12(4):365-80.


Delarue J, LeFoll C, et al. N-3 long chain polyunsaturated fatty acids: a nutritional tool to prevent insulin resistance associated to type 2 diabetes and obesity? Reprod Nutr Dev, 2004 May-Jun;44(3):289-99.


Björntorp P, Rosmond R. Obesity and cortisol. Nutrition, 2000 Oct;16(10):924-36.


Couet C, Delarue J, et al. Effect of dietary fish oil on body fat mass and basal fat oxidation in healthy adults. Int J Obes Relat Metab Disord, 1997 Aug;21(8):637-43.


Hill AM, Buckley JD, et al. Combining fish-oil supplements with regular aerobic exercise improves body composition and cardiovascular disease risk factors. Am J Clin Nutr, 2007 May;85(5):1267-74.


Thorsdottir I, Tomasson H, et al. Randomized trial of weight-loss-diets for young adults varying in fish and fish oil content. Int J Obes, 2007 Oct;31(10):1560-6.

Noreen EE, Sass MJ, et al. Effects of supplemental fish oil on resting metabolic rate, body composition, and salivary cortisol in healthy adults. J Int Soc Sports Nutr, 2010 Oct 8;7:31.