metabolism-boosting lentils

Metabolism is, as the Mayo Clinic put it, "the process by which your body converts what you eat and drink into energy. During this complex process, calories in food and beverages are combined with oxygen to release the energy your body needs to function." Any time your body does something — anything — it needs the energy from calories to do it. Basal metabolic rate (BMR) refers to the calories burned just keeping your body alive (breathing, controlling body temperature, repairing cells, etc.). We also burn calories in the process of digesting and absorbing food, known as thermogenesis. Physical activity, whether in the form of structured exercise or incidental movements like walking around your house or picking up a book, also requires calories.

When your body extracts calories from food, those calories are burned to meet the body’s current energy needs. Anything "extra" that isn’t needed right away is stored. mostly as body fat, for later use. Although doing more physical activity is the easiest way to up your body’s energy needs and burn more calories, some foods and drinks can "boost" your metabolism by creating small, temporary impacts on BMR, thermogenesis, or how many calories can actually be extracted from your food as it passes through your digestive tract. Here’s a look at some of these foods and drinks.

Coffee

metabolism-boosting cup of coffee

In addition to putting some pep in your step, coffee can boost your metabolism thanks to its caffeine content. One landmark study, published in The American Journal of Clinical Nutrition, examined the effects of caffeine on the metabolism of "lean" and "postobese" individuals. The researchers found that one 100-mg dose of caffeine (equivalent to roughly one cup of coffee) increased the resting metabolic rate of all participants by 3–4 percent over the course of 150 minutes. When given six 100-mg doses of caffeine over a 12-hour period, lean subjects burned an average of 150 more calories while postobese individuals burned an extra 79.

Another study published in the same journal noted that although caffeine didn’t seem to affect the breakdown of carbohydrates for fuel, it did seem to promote fat burning. And, when taken with food, caffeine appeared to increase the thermic effect of the meal (the number of calories the body burns just digesting food).

It’s important to note that caffeine content in coffee varies by bean and preparation. An 8-ounce cup of brewed coffee has approximately 96 mg whereas the same size serving of instant coffee only has about 62 mg. And espresso packs a big punch; a single ounce has roughly 64 mg of caffeine.

Green tea

If you prefer tea to coffee, you’ll be happy to know that it, too, boosts metabolism. For starters, both black and green tea contain caffeine, though significantly less than coffee. An 8-ounce cup of black tea has about 47 mg whereas the same size mug of green tea has 28 mg. However, green teas also contain high levels of catechins.

Catechins are a type of flavonoid, a class of chemicals found in plants that give them their color. Although found in other foods (including applies and berries), catechins are particularly concentrated in the leaves of the tea plant, from which white, green, oolong, and black tea are produced. Because of how tea leaves are processed to create black and oolong teas, however, these varieties contain minimal catechins.

A 2011 paper published in the journal Obesity Reviews found that a combination catechin-caffeine supplement increased total daily energy expenditure by about 4.7 percent. It also increased fat oxidation (burning) by 16 percent over the course of a 24-hour period. So, if you want the one-two punch of caffeine and catechins to rev up your metabolism, green tea is your best bet.

Seaweed

You can think of metabolism as a factory. The workers (the body’s cells) turn food into energy, and the thyroid gland is the foreman, supervising and regulating everything. It does this by producing two hormones: T3 (triiodothyronine) and T4 (thyroxine). These hormones affect every cell in the body and dictate how quickly or slowly that cell uses energy. Iodine is an essential component of these hormones, and the thyroid extracts and stores this mineral.

In addition to iodized table salt, seaweed is an excellent source of iodine. Amounts vary based on variety, however. According to a 2014 study published in the Journal of Food and Drug Analysis, "kombu has the highest average iodine content (2523.5 mg/kg), followed by wakame (139.7 mg/kg) and nori (36.9 mg/kg)." This means that even the minuscule amount of seaweed wrapped around your favorite sushi roll is providing a hefty dose of iodine. A quarter ounce (7 grams) of nori, for instance, provides 258.3 mcg of iodine.

The National Institutes of Health recommends that adults get 150 mcg of iodine daily to maintain proper thyroid function. But getting too much iodine can be just as dangerous as not getting enough. Adults should not exceed 1,100 mcg daily.

Brazil nuts

Selenium is a trace mineral you’ve likely never heard of, but it has an important role to play in metabolism. Men and women need 55 mcg daily, and pregnant women need 60 mcg. Selenium is found in both plant and animal foods, but Brazil nuts are by far the best source. Six to eight nuts (1 ounce) contain 544 mcg — almost 10 times the recommended daily amount. In fact, you should only eat Brazil nuts a few times a week to avoid getting too much selenium.

According to a 2017 paper published in the International Journal of Endocrinology, selenium plays two important roles in the thyroid. First, it serves as an antioxidant, protecting the thyroid against damage from free radicals. These free radicals are a natural byproduct of creating thyroid hormones but if left unchecked, they could seriously damage the thyroid. Second, selenium is a component of iodothyronine deiodinases, enzymes that can activate or deactivate thyroid hormones T3 and T4. These hormones in turn control metabolism in every cell of the body. Given selenium’s important role in the thyroid, it’s not surprising that this butterfly-shaped organ contains the highest concentration of the micronutrient anywhere in the body.

Oysters

Zinc plays an important supporting role in your metabolism, and there’s no better source than oysters. According to Healthline, six medium oysters contain 32 mg — a whopping 291 percent of the recommended daily intake. Although the thyroid uses iodine to produce the hormones that regulate metabolism, zinc is also required.

According to a paper published in 2013, zinc is needed for triiodothyronine (T3) receptors to become active. T3 is one of the two hormones produced by the thyroid that regulate metabolism, and if T3 receptors on body cells aren’t active, they can’t "accept" T3 and won’t metabolize energy correctly. Zinc deficiency has been linked to hypothyroidism (underactive thyroid), which is characterized by weight gain and a number of other unpleasant symptoms. Thyroid hormones are also necessary for the proper absorption of zinc from the diet, so hypothyroidism can exacerbate zinc deficiency, creating a vicious cycle.

According to the National Institute of Diabetes and Digestive and Kidney Diseases, hypothyroidism affects approximately 4.6 percent of Americans.

Hot peppers

When it comes to supercharging your metabolism, a little spice may be just what you need. Capsaicinoids, the chemicals that give hot peppers their kick, appear to assist weight loss in three ways, according to a 2012 study published in the journal Appetite. These include "(1) increased energy expenditure; (2) increased lipid oxidation [fat burning] and (3) reduced appetite." The authors noted that eating capsaicinoids increases energy expenditure by about 50 calories a day — an increase that would lead to "clinically significant" weight loss in a year or two. A 2018 study published in BMC Obesity similarly found that capsaicinoids "are responsible for enhanced metabolism" and reduced both body fat and fat mass.

However, capsaicinoid content varies depending on the type of pepper, ranging between 0.1 and 4.25 mg/g of pepper. The Scoville Heat Index was developed to measure capsaicinoid levels (and thus heat) in peppers. Mild-mannered bell peppers are at the bottom of the scale, at 0, while jalapeños have a rating of 2,500–8,000. The Naga Jolokia pepper clocks in at approximately 1 million, and pure capsaicin tops the scale at 15 million.

Chicken breast

There’s a reason chicken breast is beloved by both bodybuilders and dieters alike. In addition to supporting muscle growth, the high protein content in chicken breast (27 grams per 3-ounce serving) aids weight loss thanks to the thermic effect of food (TEF). As a 2014 paper published in Nutrition & Metabolism explained, "The thermic effect of food … is a metabolic response to food. Food intake results in a transient increase in energy expenditure attributable to the various steps of nutrient processing."

In other words, you’ve got to spend energy to make energy. The authors noted that TEF is measured as a percentage increase in energy expenditure above basal metabolic rate (BMR), or the calories you burn by simply existing. Protein produces the largest increase (15–30 percent), while carbs produce a more modest spike (5–10 percent) and fats produce very little (0–3 percent).

Protein is especially important when eating at a caloric deficit because it preserves muscle mass. Muscle requires more calories to maintain than other types of body tissue, so maintaining muscle mass prevents a drop in your BMR. A 2013 study in The Journal of Nutrition concluded that 1.2 grams of protein per kilogram (2.2 pounds) of bodyweight was necessary to maintain BMR while eating at a caloric deficit.

Lentils

When it comes to its metabolism-boosting abilities, not all protein is created equal. There are 20 amino acids that form the building blocks of protein, and two of them — arginine and glutamine — appear to have more of an effect on metabolism than others. Legumes are packed with protein, and lentils in particular are excellent sources of both arginine and glutamine. A 1-cup serving has 17.9 g of protein, of which 1,380 mg is arginine and 2,770 mg is glutamine (also known as glutamic acid).

A 2010 paper published in the journal Amino Acids examined arginine’s impact on bodyweight and concluded that it increased the expression of genes that regulate burning of carbohydrates, fats, and protein as fuel. It also stimulated the growth of mitochondria, the tiny "factories" inside each cell where energy is created.

As for glutamine, one 2006 study found that glutamine supplements taken alongside a meal increased energy expenditure after the meal, possibly because of glutamine’s effects on insulin. The researchers noted that immediately after the meal, breakdown of carbohydrates increased, whereas fat burning increased a bit later on.

Liver

If you can stomach it, liver can do wonders for your metabolism thanks to its high levels of B vitamins. According to Healthline, a 3.5-ounce serving contains 201 percent of your daily riboflavin (B2), 87 percent of your niacin (B3), 138 percent of your biotin (B7), and a whopping 1,386 percent of your cobalamin (B12), as well as respectable amounts of the other B vitamins.

B vitamins are vital to metabolism. As the authors of a 2020 paper published in the journal Nutrients explained, "All the B vitamins except folate are involved in at least one and often in several steps of the energy-production system within the cell." The mitochondria inside each cell need B vitamins to convert food into usable energy. Another study, published in Current Medical Science in 2018, concluded that B vitamins may reduce weight gain by improving the effectiveness of enzymes that metabolize food. In other words, B vitamins improve the body’s ability to turn food into immediate energy, reducing the chances that it gets stored as extra pounds.

If you just can’t get over liver’s strong taste and spongey texture, there are plenty of other places to get your B vitamins. Healthline recommends beef, salmon, eggs, milk, legumes, and dark leafy vegetables, among others.

Dark chocolate

Chocolate lovers rejoice! As it turns out, cacao may be as good for your metabolism as it is for your mood. In a 2014 paper published in Psychotherapy Research, a team led by Dr. Grace Farhat concluded that dark chocolate may reduce obesity by affecting the metabolism of fats and carbohydrates. This effect is achieved through several mechanisms, including "decreasing the expression of genes involved in fatty acid synthesis, reducing the digestion and absorption of fats and carbohydrates, and increasing satiety [fullness]." Dark chocolate’s high levels of polyphenols — specifically flavonoids — are likely the cause of its metabolism-boosting powers.

Polyphenols are a group of plant compounds with antioxidant and anti-inflammatory properties. Flavonoids make up about 60 percent of all polyphenols and include quercetin, kaempferol, catechins, and anthocyanins, among others. In addition to their impact on metabolism, polyphenols may also reduce your risk for cancer and heart disease, lower blood sugar levels, and improve brain function.

If you like your chocolate on the lighter and sweeter side, however, you won’t get the same slimming benefits. As the Harvard School of Public Health explained, "Dark chocolate contains up to 2-3 times more flavanol-rich cocoa solids than milk chocolate."

Coconut oil

Coconut oil is enjoying a surge in popularity thanks in large part to its high levels of medium-chain triglycerides (MCTs). MCTs, which are made up of shorter chains of carbon molecules than other types of fats, have a very different metabolic effect than long-chain triglycerides (LCTs). MCTs reduce body fat levels by decreasing the expression of genes that regulate fat storage. They’re also a preferred source of energy, easily broken down by the body for fuel. This means they’re less likely to end up stored on your midsection.

A 2003 study published in Obesity Research, for example, concluded that "consumption of a diet rich in MCTs results in greater loss of AT [adipose tissue, aka body fat] compared with LCTs, perhaps due to increased energy expenditure and fat oxidation [burning]."

According to Healthline, coconut oil is approximately 55 percent MCTs. Other dietary sources of MCTs include palm kernel oil (54 percent), whole milk (9 percent), and butter (8 percent). You can also purchase MCT oil as a supplement. MCT oil is manmade and contains high concentrations of caprylic acid and/or capric acid, the particular MCTs believed to be most beneficial.

Apple cider vinegar

If you’ve gotten on the apple cider vinegar, aka ACV, bandwagon, you may see some effects on your metabolism. There are few studies on humans, but in one, researchers gave 175 individuals a drink containing either zero, one, or two tablespoons of vinegar daily. After three months, body weight, BMI, visceral fat, waist circumference, and triglyceride levels were lower among participants who’d consumed vinegar. The study, published in the journal Bioscience, Biotechnology, and Biochemistry, noted that the acetate in vinegar appears to prevent lipogenesis (the formation of fat from glucose) and may also promote lipid oxidation (the burning of fat for energy).

If you decide to use ACV as a metabolism booster, you should be careful. Vinegar is a strong acid and should always be diluted in a lot of water. Drinking too much or improperly diluted ACV can have a number of nasty side effects, including digestive upset, erosion of tooth enamel, bone mineral loss, and burns to the esophagus.

Ginger

Spicing up your food with ginger may increase the amount of calories you burn digesting your meal. A 2013 study published in the journal Metabolism concluded that although ginger didn’t increase total resting energy expenditure (the calories we burn to keep our basic bodily processes, like breathing, chugging along), it did increase the thermic effect of food (the calories we burn as we break down food) by about 43 calories per day.

The chemical compound gingerol may give ginger its weight loss properties. A 2014 study published in the Journal of the Science of Food and Agriculture found that gingerol supplements decreased the activity of lipase (the digestive enzyme that breaks down fats) and amylase (the digestive enzyme that breaks down carbohydrates). When these enzymes are less active, the body isn’t able to extract as much energy from food as it passes through the digestive tract. Gingerol also appears to lower insulin levels. This is important because, in addition to driving glucose into body cells, insulin promotes fat storage, so keeping insulin levels low keeps body fat down. It’s important to note, however, that this study was conducted on rats, not humans.

Water

There’s a lot of hype surrounding lemon water as a metabolism booster, but it’s the water, not necessarily the lemon, doing the boosting. However, researchers differ on just how useful plain ole H2O is for revving up your metabolism.

A paper published in The Journal of Endocrinology and Metabolism found that "drinking 500 ml of water increased metabolic rate by 30%. The increase occurred within 10 min and reached a maximum after 30-40 min." The authors concluded that drinking two liters of water daily would increase energy expenditure by approximately 400 kilojoules (about 96 calories). A later study published in the same journal, however, found that room-temperature water had no effect on energy expenditure, while drinking water cooled to 3 degrees celsius (37.4 degrees Fahrenheit) only increased energy expenditure by a modest 4.5 percent over the course of an hour.

Nevertheless, the Institute of Medicine (IOM) recommends women aim for 91 ounces (2.7 liters) of fluids each day whereas men should get 125 ounces (3.7 liters). The IOM noted that not all fluids have to come from plain water, and everyone’s exact hydration requirements vary. Factors such as exercising, temperature, illness, and pregnancy can all impact fluid needs.