Low-calorie diets prove more satisfying when they include omega-3s from fish or capsules 07/07/2008
Perhaps the greatest challenge facing dieters stems from the body's built-in hunger response to deprivation.
As we reported last year, the results of a small clinical trial indicated that omega-3 fish oil supplements make very-low-calorie diets more satisfying.
In that 2007 study from Czechoslovakia, 20 obese women were randomly assigned either to a very-low-calorie diet plus omega-3 supplements, or to the same very-low-calorie diet plus placebo capsules.
After three weeks, the women taking omega-3 fish oil supplements showed significantly greater weight loss and reductions in their body mass indices (BMIs) and hip circumferences, compared with a control group.
But the small size of the 2007 Czech study precluded firm conclusions, despite fast-growing understanding of the role of omega-3s in human metabolisms.
Now, the results of a much larger trial appear to affirm the potential value of diets low in calories but high in omega-3s from fish or fish oil.
New study finds omega-3s help suppress hunger
The study published this month was part of a research project called SEAFOODplus YOUNG, funded by the European Union and intended to probe the health effects of seafood.
The new clinical trial was conducted by an international team from Iceland, Ireland, Portugal, and Spain, and involved volunteers from all four countries (Parra D et al. 2008).
As the authors wrote, "It is known that appetite sensations play a key role in the control of energy intake, therefore in the control of body weight.”
And the study's title summarizes the results obtained by the European researchers: "A diet rich in long chain omega-3 fatty acids modulates satiety in overweight and obese volunteers during weight loss.”
The researchers recruited 324 volunteers with an average age of 31 and an average BMI (body mass index) of 27.5 to 32.5 kg per square meters: height to weight measurements that classified them as overweight or obese.
All of the volunteers followed a detailed, calorie-restricted, diet plan for eight weeks.
But the participants were randomly assigned to one of four groups, whose diets provided identical amounts of calories, but resulted in them consuming relatively low or high doses of omega-3s.
Each of the diets provided the same amounts of calories, fat, carbohydrates and protein. The only significant differences were the types of fat that predominated in each diet:
Both of two "low-omega-3” diets provided no more than 260 mg per day:
- Diet 1: No seafood, plus 6 placebo (fake) fish oil capsules per day.
- Diet 2: Lean fish (150 grams of Cod 3 times per week).
Both of two "high-omega-3” diets provided at least 1,300 mg per day:
- Diet 3: Fatty fish (150 grams of Salmon 3 times per week).
- Diet 4: Fish oil capsules (6 per day).
To ensure optimal compliance with the assigned diets, each volunteer made at least three visits to a participating clinic during the trial and was contacted by phone in week two and week six.
During the last two weeks of the study, the participants answered questionnaires designed to determine how satisfied they felt by their diets.
The researchers also measured the amounts of omega-3s and other fatty acids in the participants' blood at the beginning and end of the study.
And their answers showed two encouraging results:
- People in the high-omega-3 groups had fewer, weaker hunger sensations for up to two hours after eating, compared with the volunteers on the low-omega-3 diets.
Participants with higher omega-3/omega-6 ratios in their blood reported fewer, weaker hunger sensations for up to two hours after eating.
As the authors wrote, "…subjects who eat a dinner rich in long chain omega-3 fatty acids feel less hunger and more full directly after and 2 hours after.... This observation indicates that long chain omega-3 fatty acids modulate hunger signals” (Parra D et al. 2008).
And one comment they made gets to the heart of the matter: "The usefulness of long chain omega-3 fatty acids in the nutritional treatment of obesity has to be investigated further, since they could improve the patients' compliance to changes in dietary habits required for weight loss and weight loss maintenance” (Parra D et al. 2008).
In other words, low-calorie diets may be easier to follow if they are high in omega-3s and low in omega-6s, which predominate America's most commonly consumed vegetable oils (corn, soy, safflower, soy, canola).
To cut back on omega-6s, avoid these oils, the packaged and take-out foods made with them, and standard, grain-fed meats and poultry.
Instead, use extra virgin olive oil, hi-oleic sunflower oil, or macadamia nut oil, and look to fish and grass-fed meats or poultry for protein.
How might omega-3s moderate appetite or aid weight control?
Why would EPA and DHA—the long-chain marine omega-3s found only in fish and algae—aid weight control efforts?
Our search of the scientific literature uncovered at least seven ways in which the omega-3s in fish and fish oil might help:
- Stimulate secretion of leptin, a hormone that decreases appetite and promotes the burning of body fat.
- Enable burning of dietary fats by helping move fatty acids into body cells for burning as fuel.
- Encourage the body to store dietary carbohydrates in the form of glycogen, rather than as hard-to-lose body fat.
- Dampen inflammation, which is known to promote weight gain.
- Enhance blood-sugar control by increasing our insulin-producing cells' sensitivity to sugar.
- Flip off genetic switches (nuclear transcription factors) that promote inflammation and storage of food as body fat.
- Help the body transport glucose from blood to cells by increasing the fluidity of cell membranes.
This excerpt from a recent Japanese report adds more illuminating evidence: "We recently reported that omega 3 … from Salmon roe prevented the development of obesity-related diseases through the suppression of lipogenic [fat-storing] gene expressions and the enhancement of lipolytic [fat-burning] gene expressions in the liver of obese rats” (Yanagita T, Nagao K 2008).
For more on the subject, see "Exercise + Omega-3s = Perfect Weight Loss Pair”.
- Gunnarsdottir I, Tomasson H, Kiely M, Mart?nez JA, Bandarra NM, Morais MG, Thorsdottir I. Inclusion of fish or fish oil in weight-loss diets for young adults: effects on blood lipids. Int J Obes (Lond). 2008 May 20. [Epub ahead of print]
- Mori TA. Effect of fish and fish oil-derived omega-3 fatty acids on lipid oxidation. Redox Rep. 2004;9(4):193-7. Review.
- Mori TA, Burke V, Puddey IB, Shaw JE, Beilin LJ. Effect of fish diets and weight loss on serum leptin concentration in overweight, treated-hypertensive subjects. J Hypertens. 2004 Oct;22(10):1983-90.
- Parra D, Ramel A, Bandarra N, Kiely M, Mart?nez JA, Thorsdottir I. A diet rich in long chain omega 3 fatty acids modulates satiety in overweight and obese volunteers during weight loss. Appetite (2007). doi:10.1016/j.appet.2008.06.003
- Ramel A, Martinéz A, Kiely M, Morais G, Bandarra NM, Thorsdottir I. Beneficial effects of long-chain n-3 fatty acids included in an energy-restricted diet on insulin resistance in overweight and obese European young adults. Diabetologia. 2008 Jul;51(7):1261-8. Epub 2008 May 20.
- Yanagita T, Nagao K. Functional lipids and the prevention of the metabolic syndrome. Asia Pac J Clin Nutr. 2008;17 Suppl 1:189-91. Review.