I walked into Panera the other day and I let it slip out to the chatty guy behind the counter that I’m a psychologist. He seizes what he sees as an opportunity for advice and asks me to weigh in on his love life (insert laugh track). What should I do, doc??? I start to panic on the inside, but then without even hesitating, I responded: ACAI BERRIES!
Well, they ARE a SUPER food after all. Super foods! They are the cure for everything from broken hearts to cancer to obesity. I am fascinated by the “super” food industry, especially how super foods go in and out of fashion over time. I am particularly fascinated when the “super” claims include weight loss. Are super foods “fat burning,” “metabolism-boosting,” weight loss jackpots? If it were that simple, why aren’t we all skinny?
For insight, let’s consider the two miracle foods du jour: acai berries and green tea.
Acai berries grow on Acai Palm trees in Central and South America. They are small round purplish berries that are not as sweet as most berries, somewhat bland when eaten alone but add flavor to other foods. A quick Google search reveals thousands of sites peddling acai berry juice, powder, pills, chews, and suppositories (just kidding!) for weight loss. I go to GNC.com. A 32 ounce bottle of Acai berry juice is a whopping $35. I’m no mathematician but are you telling me that if I drank a bottle every other day, the acai berry juice diet would cost me $560 per month? For that price point, I think I’d prefer to buy a Cadillac Escalade, the giganticness of which will instantly make me appear 10 pounds smaller. Are acai berries worth the price?
Acai berries are valued for their high antioxidant content. Antioxidants are awesome because they slow the process of oxidation and cell damage, thus slowing aging and reducing the risk of cancer and cardiovascular disease. Foods rich in antioxidants play an important role in a healthy diet for this reason. Interestingly, the antioxidant content of Acai berries is not higher than common and less expensive fruits such as mangoes, strawberries and grapes. Acai berry juice has also been found to have lower antioxidant content than red wine, and grape, cherry, and blueberry juices (Seeram et al 2008), which are cheaper and more accessible. And the worst news about the acai berry is that unlike other berries, its composition is 50% fat (insert screams). Fatty fruit!? Finally, in my search of Pubmed.gov (the database of nearly all published research reports in existence), there is not a single randomized trial testing the impact of a diet rich in acai berries on weight loss. I’m puzzled. You too?
Perhaps there is more hope for green tea? Green tea originates from China, but mass marketed in the US, so it is reasonably priced with 40 tea bags ringing up at $6.50 (whew!). But if you insist on being the big spender, go to GNC and pick up a bottle of GNC Herbal Plus Green Tea Complex 200 capsules for $38.
Can green tea help me lose weight? The active “weight loss” ingredient of green tea is a tea polyphenol (which acts like an antioxidant) called ECGC (epigallocatechin gallate). When mixed with caffeine, ECGC has been shown to increase the rate at which your body burns calories (i.e., metabolism). This metabolic effect has been established in animal and human laboratory studies, but only clinical trials in humans can establish an actual weight loss effect. A review that summarized the results of 11 clinical trials on the effect of green tea on weight loss in humans concluded that green tea can have a modest impact on weight (Hursel et al 2009). The story is kinda complicated though. The size of the impact may depend on your caffeine consumption and whether or not you are Asian. People with moderate to high caffeine intake lost less to no weight from green tea compared to people who typically consumed very little caffeine. Also, the majority of trials were performed in Asian adults, which had consistently positive results, whereas the few studies in Caucasian adults had mixed outcomes, from some weight loss to none at all. So, if you are Caucasian and drink moderate to high amounts of caffeine, green tea might not be all that helpful for weight loss. If you are Latino or African American, then we have no idea how your body will respond because none of the studies included enough people with these ethnic backgrounds. I should also mention that studies of green tea on weight loss routinely put their participants on a low-calorie diet, so the weight loss in these studies reflects the advantage of green tea plus low-calorie diet relative to low-calorie diet alone. A final note is that the average weight loss advantage of green tea across all studies was about 2-4 pounds over 2-3 months of dieting. Yes, it is an effect and it is statistically significant, but I don’t think it’s blowing you away right now.
The bottom line is that super foods are super good for your health but do not necessarily impact your weight (although in some cases your wallet may lose weight). The impact of “metabolism boosting” foods is likely to be very small, especially in proportion to the hype. In fact, it is highly unlikely that we will discover a true “weight loss” food. Keep this in mind before spending your money on the host of products marketed by exaggerated claims. One teeny tiny study is enough to create a million dollar industry for supplements, books, food products, you name it. A better approach is to invest in your local farm stands and farmers markets which are filled with super good foods that can supplement a healthy diet in which total calories consumed is less than the amount expended.
Or, you can always buy that Escalade…
Seeram, NP, Aviram, M., Zhang, Y, Henning, SM, Feng, L., Dreher, M, Heber, D. Comparison of antioxidant potency of commonly consumed polyphenol-rich beverages in the US. Journal of Agric Food Chem, 56(4): 1415-1422.
Hursel, R, Viechtbauer, W., Westerterp-Plantega, M.S. (2009). The effects of green tea on weight loss and weight maintenance: A meta-analysis. International Journal of Obesity, 33, 956-961.
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