We’ve all seen the headlines singing the praises of one fat-melting food that will rev up metabolism or somehow magically melt away extra pounds. Sure—it would be nice if there were a silver bullet that transformed our bodies into lean, mean, digestion machines. But unfortunately, most products that claim to be “cleansing” don’t actually cause you to suddenly drop ten pounds.
That’s not to say foods don’t affect your metabolic system at all. For example, hot peppers and green tea have both been shown to boost metabolism, albeit slightly. We dug into the science to understand the nuances behind those dramatic headlines and serve up some truth about food and metabolism.
What is metabolism?
Metabolism refers to any bodily process that uses energy, including digestion, breathing, circulation, controlling body temperature, muscle contraction, and brain and nerve function. The body expends a certain number of calories to perform these functions, which is otherwise known as resting metabolic rate.
There is much debate as to whether your resting metabolic rate is set in stone or can be altered. “In a way, every food will increase metabolism because it needs to be broken down,” says Mascha Davis MPH, RDN, owner of Nomadista Nutrition. “The speed of our metabolism is largely outside of our control and plays only a minor role in weight management,” Davis adds. Still, some research points to the fact that adding muscle mass and eating certain foods can alter metabolism speed—but the results may not be as dramatic as the sensationalized claims we hear all too often.
Many believe that sipping a cup of green tea revs up your metabolism, but that’s only partly true. One meta-analysis found that drinking green tea in conjunction with reducing calories resulted in weight loss. The researchers attribute this positive impact largely to EGCG, a compound in the tea which—when combined with caffeine and on its own—is believed to promote fat oxidation. But one has to wonder if the study participants lost weight primarily because of their green tea intake or more so because they were cutting calories.
Regardless, adding a glass of green tea to your daily routine sounds like a no-brainer, but the amount used in clinical settings tends to be much higher than an average glass. In the aforementioned study, participants received an average of 250 milligrams of green tea, or 3 cups, which helped to burn 100 calories. We’re not knocking an extra hundred calories—but to put that into perspective, that equates to about one measly ounce of cheese.
We’ve all heard the rumors that drinking cayenne and lemon water will crank up your metabolism like crazy. That’s probably a little far-fetched, but there is some evidence that capsaicin (the compound found in hot peppers) may boost metabolism. Here’s the caveat—most studies use an alarmingly large amount of cayenne pepper. For that reason, a recent randomized controlled trial looked at the effects of eating a palatable amount of cayenne, about 1 gram or a ½ teaspoon, and its effects on metabolism. The researchers found that this amount typically used in recipes only burns about 10 calories. So go ahead and have 2 more tortilla chips—you deserve it!
A study in the American Journal of Clinical Nutrition looked at how substituting whole grains for refined grains might affect metabolism, and the results were actually pretty promising. For 8 weeks, the study’s participants ate either 200 grams of whole grains with 40 grams of fiber, or no whole grains with just 20 grams of fiber. In the end, the participants on the whole-grain diet burned an extra 45 calories. Though the difference is small, it’s yet another reason to choose whole grains.
According to Davis, meals higher in protein or fiber typically take more energy to digest—meaning they might amp up overall energy expenditure. As a matter of fact, about 20-30 percent of the energy from a standard protein meal is used in the digestion process, while fat and carbs only need 5 percent of calories for digestion. That means for every 100 calories of protein you consume, 20 to 30 are burned off in the digestion process. While this sounds exciting, let’s be realistic about what 20 calories really looks like—2 stalks of celery, 1 carrot, or 1 tomato.
“Moderate caffeine intake has been shown to temporarily increase an individual's metabolic rate between one to 25 percent,” says Kristen Smith, MS, RD. However, she suggests holding off on the extra-large coffee. “Large intakes of caffeine can result in health consequences such as a rapid heart rate, digestive issues, or insomnia,” Smith says. She also adds that drinking a ton of coffee may displace other much-needed nutrients from your diet, like protein, fat, carbs, vitamins, and minerals. So while that cuppa joe might be a convenient way to wake up all the systems in the a.m., it shouldn’t be the only thing you put into your body.
This oil’s claim to fame is that it contains medium-chain triglycerides (MCT), which are thought to be stored in the body less easily than other types of saturated fat. Unfortunately, research has proven that eating medium-chain triglcyerides instead of long-chain triglycerides doesn’t really make much of a difference when it comes to your waistline.
The Bottom Line
“Unfortunately, no single food is going to magically boost your metabolism,” Smith says, and the research concurs. “The downside of such claims is that people might rely on the ‘fat-burning’ effect of certain food instead of making sustainable dietary changes,” Mascha adds.
Even though green tea or cayenne pepper may help you burn an extra 20-50 calories, neither is likely to make a huge difference in your overall weight. According to the experts, the key to a healthier weight is eating a balanced diet composed of nutrient-dense foods. Yup—good old healthy eating and moderation come out on top yet again.