The list of beneficial properties of omega-3 fatty acids (fish oil) is enormous. They are essential for the health of the cardiovascular system, brain, and eyes, protect against depression and aggression, make the skin healthier, and have anti-cancer effects.
In the material What are the benefits of omega-3 fatty acids. Scientific research, dedicated to reviewing the advantages for which omega-3 is taken and which have scientific justification, we also mentioned the benefits of omega-3 for weight loss, with some caveats.
In this article, we will take a closer look at the effectiveness of omega-3 for weight loss based on scientific research.
Main thoughts:
Brief Introduction to Omega-3
Omega-3 fatty acids are a type of fat that is vital for human health. They are essential and must be included in the diet.
There are three main forms of omega-3. Not all of them are equally effective and beneficial:
ALA (Alpha-linolenic acid)
It is an essential inactive form of omega-3 that must be converted in the body into the active forms DHA and EPA. The efficiency of this conversion is very low: only 5-10% of ALA is used to create DHA and EPA 1.
Essential in this context means that the body cannot synthesize them on its own, so they must be obtained from food.
Omega-3 in the form of ALA is found in a wide range of natural plant products, including walnuts, flaxseeds, hemp seeds, chia seeds, as well as their oils.
DHA and EPA
DHA (docosahexaenoic acid) and EPA (eicosapentaenoic acid) are two active forms of omega-3 that are directly responsible for their beneficial properties.
They are found in fatty fish, shellfish, and algae (phytoplankton).
These forms can be synthesized from ALA fatty acids, so by definition, they are not essential; however, the efficiency of conversion is very low.
Therefore, doctors and scientists recommend taking at least 200-500 mg of omega-3 in the form of EPA and DHA every day in the form of fish oil, krill oil, or microalgae supplements, or consuming fatty fish at least twice a week.
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Omega-3 in the form of EPA and DHA are components of cell membranes and play a particularly important role in the functioning and development of the brain and visual system 2,3.
They also have anti-inflammatory effects, improve memory and concentration, have anti-cancer properties, and are beneficial for the heart.
Many diseases in the body are accompanied by inflammatory processes, so the ability of omega-3 to reduce inflammation explains many of their beneficial properties. For more information on the benefits of omega-3 for health, read the article What are the benefits of omega-3 fatty acids? Scientific research.
Not all omega-3s are equally beneficial. Omega-3 in the form of EPA and DHA are active and responsible for their beneficial properties. Their sources are fatty fish, algae, and supplements based on them. ALA is an inactive form of omega-3 from plant oils and seeds; it is less beneficial as it converts to active forms with low efficiency.
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Scientific Facts About the Benefits of Omega-3 (Fish Oil) for Weight Loss
1 Omega-3s May Reduce Appetite and Feelings of Hunger
Suppressing appetite and feelings of hunger is one of the mechanisms of action of various weight loss supplements, foods, or substances.
When consuming omega-3s with food, some people report feeling full more quickly and a corresponding decrease in the amount of food consumed (= calories). However, this does not always happen.
In one study, one group of healthy individuals consumed less than 0.3 g of omega-3 per day, while another group consumed 1.3 g. Those who took higher doses of omega-3 reported a significantly greater feeling of fullness two hours after eating 4.
However, it is well known that any sensations are subjective and cannot be measured. Therefore, it is not surprising that there are experiments with opposite results.
When healthy adults not following a special weight loss diet took 5 g of omega-3 (fish oil) every day, their feelings indicated that fullness was 20% less, and the desire to eat was 28% stronger than in the group that did not take fish oil 5.
Similar results were found in experiments involving patients with cancer or kidney problems: omega-3s stimulate appetite, leading to a higher caloric intake 6, 7, 8.
What is even more interesting is that one study showed that taking omega-3 fish oil increases the level of the hormone signaling fullness in obese individuals but decreases it in those with normal weight 9.
That is, the benefits of omega-3s for weight loss regarding their influence on appetite and fullness are likely to be individual and determined by health status, degree of obesity, and diet.
Omega-3 (fish oil) may be effective in suppressing appetite in obese individuals as well as healthy people on a calorie-restricted diet; in some cases, adding it to the diet may have the opposite effect, stimulating appetite.
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2 Omega-3 (fish oil) may increase metabolic rate
Increasing metabolic rate is another possible mechanism of action for omega-3 in weight loss.
The metabolic rate determines the number of calories the body needs to maintain vital functions. It is sometimes referred to as resting metabolism: calories expended on physical movements are not included.
The higher the metabolic rate, the more calories are burned each day, and the more effective the fat-burning process.
About 70% of the calories burned each day come from basal metabolism, while the remaining 30% are for maintaining physical activity and sports. Clearly, sports account for a very small portion, and therefore any type of sport is extremely ineffective for weight loss. Explanations can be found in the material What to do to lose weight or Why a proper diet is more important than sports.
In one study, it was shown that when healthy young individuals took 6 g of omega-3 (fish oil) per day for 12 weeks, their metabolic rate increased by an average of 3.8% 10. This figure is not very impressive, especially considering the margin of error in such measurements.
In another study, where healthy elderly women took 3 grams of fish oil per day for 12 weeks, their metabolic rate increased by 14%, which is equivalent to about 187 calories per day 11.
In terms we can understand, 187 calories is roughly equivalent to about a third of a chocolate bar or a slice of bread… Not much, but still. Life is made up of small things.
In many studies, researchers note a clear correlation between increased metabolic rate and increased muscle mass. Muscles require more energy to maintain their state than fat. That is, the more muscle mass in the body, the more calories are burned even at rest.
This explains the benefits of strength training for weight loss: during a standard bodybuilding workout, very few calories are burned, but the increasing muscle mass boosts the resting metabolic rate.
Omega-3 (fish oil) may increase metabolic rate. The higher the internal metabolic rate, the more calories are burned even at rest, making weight loss more effective.
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3 Omega-3 may enhance fat burning during exercise
The theoretical justification for the benefits of omega-3 fatty acids for weight loss is that they enhance the function of carnitine in transporting fats from storage (“bellies,” “thighs,” and “butts”) into cells for use as energy. This is a kind of switch from using carbohydrates for energy to fats 12.
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Scientific studies indicate that the consumption of omega-3 may indeed increase the number of calories and fat burned during exercise.
In one study, it was shown that when women took 3 g of omega-3 (fish oil) per day for 12 weeks, they burned 10% more calories and 20-27% more fat during exercise each day 13.
Experiments show a clear pattern indicating that omega-3 + exercise is more effective for weight loss than exercise alone 14.
However, this is one side of the story. In a number of other experiments, the influence of omega-3 on accelerating fat burning for energy during exercise is NOT confirmed 15, 16.
Omega-3 (fish oil) may increase the number of calories and fat burned during exercise, but scientific research on this is ambiguous.
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Omega-3s may be beneficial for weight loss, but not for reducing weight…
And now, when some are inspired and others inevitably disappointed by the perceived uselessness of omega-3s for weight loss, it is time to remind about theimportant distinction between weight loss and reduction of body fat percentage.
Often both are referred to as “weight loss,” as we are all used to tracking weight loss progress by the scale readings. However, no one will argue that reducing body fat percentage is more significant, which can sometimes occur without any change in body weight.
For example, strength training is beneficial for weight loss (fat burning), but at the same time, its “side effect” is an increase in muscle mass. Together, these two processes improve body composition, but may not affect weight, as muscle mass increases alongside a decrease in fat mass.
Practical takeaway: do not use the scale to track weight loss progress; measure skinfold thickness, waist and hip circumference, or body fat percentage.
A similar situation can be observed with omega-3s: they may be beneficial for weight loss in terms of reducing body fat percentage, but the negative result of their impact on body weight in many scientific studies can be explained by the simultaneous increase in muscle mass.
This is particularly evident in well-designed experiments where researchers carefully measure multiple parameters.
For example, in one study where 44 people took 4 g of omega-3 (fish oil) daily to lose weight, no effect was noted: body weight did not change.
However, compared to the control group that did not take omega-3, the body fat mass in the fish oil group decreased on average by 0.5 kg, while muscle mass increased by the same amount (0.5 kg) 17.
In another study, when 6 grams of fat in the diet of healthy adults were replaced with 6 g of fish oil for three weeks, body weight also did not change, but body fat mass decreased 18.
Similar results are found here 19.
In one of the reviews of several dozen scientific studies on the effectiveness of omega-3 for weight loss, researchers noted that omega-3 is ineffective in reducing body weight but helps to decrease waist circumference and the ratio of waist to hip circumference 20.
Omega-3 (fish oil) may be ineffective for weight loss in terms of reducing body weight, but effective in reducing body fat percentage and related metrics (waist circumference, skinfold thickness)
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How to take omega-3 for weight loss
Recommendations regarding the daily dose of omega-3 vary among different authoritative organizations and range from 500 to 3000 mg per day.
This discrepancy is partly due to the fact that in scientific experiments, the beneficial properties of omega-3 are demonstrated at different dose values. And the rule “the more, the better” does not apply here.
On the contrary, the upper limit is very important and should not be exceeded, as omega-3 has a blood-thinning effect and its overdose can lead to excessive bleeding in some individuals, especially those taking medications to reduce blood viscosity.
Also, certain omega-3 supplements (such as cod liver oil) contain a significant amount of vitamin A, and an overdose of which can be dangerous to health.
For detailed instructions on taking omega-3, read the article How to properly take Omega-3: instructions for use, daily dosage, harm.
For maximum health benefits and weight loss, it is recommended to take 500-3000 mg of omega-3 per day. The rule “the more, the better” does not apply here. High doses can lead to blood thinning and vitamin A overdose
Conclusion
The benefits of omega-3 for weight loss do not have unequivocal scientific confirmation.
These fatty acids may accelerate satiety and reduce appetite, thereby decreasing the number of calories consumed, but they can also have the opposite effect.
There is evidence of omega-3’s ability to activate the rate of internal metabolism at rest, as well as the amount of fat burned during exercise.
A possible reason for the negative results in studies on the effectiveness of omega-3 for weight loss in many experiments is that researchers measure body mass as a criterion, which does not change because, simultaneously with the reduction of fat mass, there is an increase in muscle mass.
Most scientific studies indicate a positive effect of omega-3 on body composition: a decrease in body fat percentage, waist circumference, and skinfold thickness, while simultaneously increasing muscle mass.
However, do not forget: omega-3 is not a fat burner. Trying to solve the problem of excess weight by consuming liters of flaxseed oil or fish oil is a bad idea.
Excessively large daily doses of omega-3 can be harmful to health, and the effect shown by scientists for weight loss is equivalent to… a few cookies.
