Some people envy others for their fine jewelry or luxury cars, I covet fast metabolisms. I am practically star-struck watching my friend’s lean 17-year-old son regularly plow through piles of food, totally carefree (especially because his parents are buying the groceries).
My personal calorie-burning engine is about average, so although I’d like to say I have higher-minded reasons, truthfully what gets me to the gym most days is the reward of being able to eat more. But working out takes time and effort. What if you could burn calories without breaking a sweat, simply by eating certain foods? It’s an irresistible idea that gets a lot of media attention.
About 81 million search results come up when you Google “metabolism boosting foods,” with slide shows, books, blog posts, articles, podcasts and more pointing out what to eat to burn more calories. Predictably, most claims, if not unfounded, are overhyped, over-extrapolated half-truths. I laughed out loud reading some of these pieces — one justified its recommendation to eat sunflower seeds to burn belly fat with a link to a study done on 144 broiler chickens. Seriously, broiler chickens. But, it turns out, some foods and drinks do have solid science behind them as likely metabolism boosters in humans. Even those with the most evidence won’t transform you into a calorie-burning machine — but they might make some difference and are worth considering.
One of the tricky things about making sense of these claims is that metabolism is very broadly defined. My Stedman’s Medical Dictionary says it is “the sum of the chemical changes occurring in tissue.” So, technically, anything that happens in your body is part of your metabolism. But I am zeroing in on a definition of metabolism most of us have in mind when we complain of ours being slow: the number of calories we’d burn in a day if we were just sitting on the sofa. That number is the sum of our basal metabolic rate, the calories the body burns carrying out basic functions such as breathing and repairing cells; and thermogenesis, the calories expended to digest and process food. There is evidence that certain foods and drinks can bump up that total. Physical activity is a third factor contributing to our overall daily calorie burn. It is the most variable factor, and the one we have the most control over.
Green tea is the most celebrated metabolism-boosting consumable, and for good reason. Many studies confirm that the polyphenols called catechins (especially epigallocatechin gallate, or EGCG) and caffeine in green tea increase the calories and fat you burn. A 2011 meta-analysis published in Obesity Reviews found that supplementation with catechins and caffeine mixtures increased energy expenditure by an average of 100 calories a day. But here’s the fine print: The amount of EGCG consumed in the studies ranged from 122 and 1,200 milligrams a day, with about 250 milligrams the most commonly administered amount.
According to a report by ConsumerLab.com, the EGCG content of commercially available teas varies widely, from 25 to 86 milligrams per serving. So you’d need to drink about three cups of the highest-quality tea daily to get 250 milligrams of EGCG. That seems doable, and there are other health benefits of drinking green tea, so as long as you keep in mind that it has caffeine, and you don’t add sugar to it, there’s probably no downside. But if you are considering it as a way to help you lose weight, it might not be the answer you seek. Studies have been mixed as to whether drinking it translates to weight loss — a 2012 report by Cochrane that examined 15 studies showed no significant effect on weight over the long term.