Abstract
The use of food supplements for weight loss purposes has rapidly gained popularity as the prevalence of obesity increases. Navigating through the vast, often low quality, literature available is challenging, as is providing informed advice to those asking for it. Herein, we provide a comprehensive literature revision focusing on most currently marketed dietary supplements claimed to favor weight loss, classifying them by their purported mechanism of action. We conclude by proposing a combination of supplements most supported by current evidence, that leverages all mechanisms of action possibly leading to a synergistic effect and greater weight loss in the foreseen absence of adverse events. Further studies will be needed to confirm the weight loss and metabolic improvement that may be obtained through the use of the proposed combination.
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Key Points
Results from reviews and metanalyses show that flaxseed consumption has beneficial effects on blood pressure, lipid profile and glucose metabolism. A 2017 review and metanalysis including 45 RCTs, highlighted the effect of flaxseed supplementation on body weight and body composition. Interestingly, only whole flaxseed was able to reduce body weight, BMI, and waist circumference, while flaxseed oil and lignans extracts did not show any benefit. Furthermore, a significant weight loss was observed only in subjects with BMI >27, eating more than 30 gr of flaxseed per day and in trials longer than 12 weeks. These findings suggest that the high fiber content or other compounds present in whole flaxseed are responsible for the higher weight loss. These results may also indicate that flaxseed supplementation has a cumulative and time dependent effect, probably because ALA, lignans or other flaxseed components build up their concentration in tissues over time or because of gut microbiota adaptations happening over a longer period. Among the studies analyzed, only few studies incorporated lifestyle advice or provided hypocaloric diets, and no data were reported regarding daily caloric intake, making it difficult to understand the mechanisms behind the weight reduction. Furthermore, the high heterogeneity of the studies regarding study populations (healthy subjects and subjects with different comorbidities) may hinder the results strength.
This study found that flaxseed showed promising weight reduction properties, backed by numerous health benefits, although the quality of the evidence supporting its application for this purpose is still low; however, considering the absence of side effects, its consumption may be considered for the treatment of obesity. To further understand the mechanisms promoting weight loss, studies analyzing appetite parameters alongside changes in daily caloric intake and gut hormones levels over time are needed.