While a balanced, reduced-calorie diet and exercise is the best way to lose weight, some foods, beverages and supplements may give you a slight weight-loss boost when used alongside diet and exercise. This may include certain types of seaweed supplements, although research is still in the preliminary stages. Check with your doctor before taking seaweed pills to make sure these would be safe for you.
Fucoxanthin and Weight Loss
Some types of seaweed supplements may be helpful for slightly increasing weight loss. A study published in Diabetes, Obesity and Metabolism in January 2010 found that a supplement containing fucoxanthin from brown algae and pomegranate-seed oil helped increase weight loss and decrease body fat in overweight women. Potential mechanisms include increasing energy expenditure and limiting deposits of body fat. It's not yet known how much of this benefit came from the seaweed extract and how much came from the pomegranate seed oil, however.
Alginates and Weight Loss
Alginates, which are substances found in brown seaweed like kelp, may help limit the digestion and absorption of fat in the body, thus improving weight loss, although research is still preliminary. A 12-week study published in the American Journal of Clinical Nutrition in July 2012 found that alginate supplementation before each meal may help improve weight loss when combined with a reduced-calorie diet.
Not all studies show a beneficial effect with alginate supplementation, however. A study published in Obesity in August 2010 found no effect on appetite, satiety or dietary caloric intake when overweight women took alginate supplements for 10 days. A two-week study published in Appetite in December 2011 came to a similar conclusion, noting that alginate supplements didn't result in an increase in weight loss over a reduced-calorie diet alone.
Enhancing the Effects
Seaweed pills may be more effective for weight loss if you're also getting enough good fats in your diet. For example, an animal study published in the Journal of Agricultural and Food Chemistry in 2007 found that the seaweed extract fucoxanthin was more effective for limiting weight gain when it was combined with fish oil. Another animal study, published in Archives of Biochemistry and Biophysics in March 2012, found that this same seaweed extract improved fat metabolism and helped limit weight gain from high-fat diets when taken in conjunction with conjugated linoleic acid, a type of polyunsaturated fat.
A mix of monounsaturated fat and fucoxanthin may also be more beneficial for limiting abdominal fat than either of these substances alone, according to an animal study published in the Journal of Oleo Science in 2007. Further research is necessary to verify these same effects occur in people and whether they occur with other types of seaweed supplements as well.
Some types of seaweed are high in vitamin K and thus are not recommended for people taking blood thinners. Seaweed can sometimes be high in iodine, so taking too many seaweed supplements may cause an increase in thyroid-stimulating hormone. Excessive intakes of seaweed may also cause your skin to develop a yellow color.