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Protein-rich foods -

Protein has a strong reputation among body builders and other fitness-conscious folk, and with good reason. Your body uses more energy to digest protein-rich foods such as eggs, meat, fish, and legumes than to digest carbs and fat, and protein can also help you feel fuller for longer.

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Selenium-rich foods - Studies suggest that the minerals selenium and iron can have a significant effect on the functioning of the thyroid gland, which regulates your metabolism. Selenium-rich foods, like Brazil nuts and sardines, can help your thyroid function as well as possible.

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Iron-rich foods -

A diet that is too low in selenium or iron can prevent the thyroid from producing the right amount of hormones, which could slow down your metabolism. Including plenty of iron-rich food like spinach and broccoli can give your thyroid a helping hand.

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Beans and legumes -

Foods such as lentils, chickpeas, beans, and peas are a powerhouse for the metabolism. Rich in iron and energy-burning protein, they also contain dietary fiber, which the body can use as a prebiotic. These gut-friendly bacteria produce short-chain fatty acids, which can help the body burn fat as energy, and regulate sugar levels.

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Seaweed -

Seaweed is a potent source of iodine, another mineral that aids the proper functioning of the thyroid gland and the production of thyroid hormones. It's also packed with iron, and some types of seaweed contain fucoxanthin—a compound that studies suggest can promote metabolic health.

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Apple cider vinegar -

Studies suggest that the acetic acid in apple cider vinegar could help aid weight loss. A short-chain fatty acid, it may boost the body's ability to use fat as energy, and lower blood sugar levels. But go easy, or you could cause damage to teeth and stomach lining. One or two tablespoons per day, diluted in a cup of water, is ideal.

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Cacao and cocoa -

Although there's no hard and fast evidence that cocoa, cacao, and dark chocolate can increase your metabolic rate, studies in animals suggest they might speed up fat burning, and improve digestion. They're rich in antioxidants, and raw cacao is particularly high in protein, iron, and fiber.

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Ginger -

Fiery ginger can apparently help fire up the metabolism. Studies suggest that drinking ginger powder in hot water with a meal can burn more calories than the hot water alone, and the warming drink may also help you feel fuller and decrease hunger levels.

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Coffee -

Good news for coffee lovers: studies show that the caffeine found in your morning cup of java could boost metabolic rate. Don't overdo it though, or you might get the jitters. But some studies suggest that drinking around three cups of coffee per day could help burn an extra 100 calories per day. It's also thought to help the body use fat as energy, and can have a positive impact on workout performance.

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Tea -

Coffee not your thing? Tea has you covered. Together with the caffeine, health-boosting catechins found in certain types of tea may help boost metabolic rate. Studies suggest green tea and oolong tea may increase the body's fat-burning capacity by as much as 17%. Drink up!

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Matcha tea -

Along with oolong, tea, healthy matcha green tea is thought to help increase fat oxidation and burn extra calories when exercising.

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Water -

Drinking plenty of water is essential to staying hydrated, and it might even temporarily boost metabolism by as much as 30%. Researchers say the increase may be partly down to the body expending energy in raising water to body temperature, known as "water-induced thermogenesis."

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MCT oil -

Often derived from coconuts and typically taken as a supplement or added to smoothies, medium chain triglyceride (MCT) oil is thought to help increase metabolic rate in humans. Unlike the short-chain fats commonly found in processed foods, MCTs are easily converted into energy, making them less likely to be stored in the body as fat. They also contain the satiety hormone ghrelin, helping you to feel full and consume fewer calories.

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Avocado -

Avocado is high in healthy fats, which can help promote feelings of fullness. One study showed that adding half an avocado at lunch could help reduce people's desire to consume more food in the hours after a meal. But don't go crazy: avocados are pretty high in calories, as well as being high on the 'unsustainable foods' list.

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Eggs -

High in satiating protein, eggs are also rich in B vitamins, which helps convert food into energy. Just resist the temptation to add loads of butter, salt, or cream. Poached or boiled eggs are a good bet.

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Whole grains -

Swapping refined bread and pasta for whole grain varieties could help with weight management. The fiber in wholegrains helps you feel full, and a 2017 study from the American Journal of Clinical Nutrition suggested that switching from refined grains to whole grains could cause a "modest increase" in resting metabolism.

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Chili peppers -

Firing up your body with chili peppers could help boost the rate at which it burns calories. It's thought that the chemical capsaicin, found in chilis, can reduce calorie absorption, and help the body burn fat.

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Tempeh -

A great source of vegan protein, tempeh is full of proteins and healthy fat, which can help you feel full. Made with fermented soybeans, it contains probiotics, which can help boost gut health and energy levels overall.

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Omega-6 fatty acids -

Not to be confused with the healthy omega-3 fatty acids found in nuts, seeds, and eggs, omega-6 fatty acids have been linked to weight gain and decreased metabolism. Soybean oil is a common source, so switch to alternatives like flax oil or olive oil.

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Granola and granola bars -

Frequently marketed as a health food, granola is often anything but healthy. It's typically high in calories, fat, and sugar, with the latter causing blood sugar spikes that can make you feel hungrier. Look for sugar-free, oil-free options made with whole grains, and without too much dried fruit.

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Alcohol -

Booze are high in empty calories, and can also affect judgment and lead to poor food choices. Not only will a few drinks wipe out your evening exercise plans, but alcohol can often leave people feeling sluggish, unmotivated to exercise, and craving junk food the next day.

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Sugary drinks -

Non-alcoholic drinks don't get off so lightly, either. A 2017 study published in the journal BMC Nutrition showed that consuming a high-sugar drink along with a high-protein meal could reduce fat metabolism, and cause the body to store more fat.

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Fruit juice -

Fruit juices are high in calories, and the juicing process takes healthy fiber out of the fruit. As a concentrated form of sugar, 'healthy' fruit juice can increase blood sugar, and stimulate hunger pangs.

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Non-organic fruits and vegetables -

Reaching for an apple? You might want to think twice. Some fungicides used on fruit and vegetables have been shown to cause weight gain in mice, and researchers believe they could have a similar effect on humans. Go for organic, and always wash your fruit and vegetables.

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'Dirty dozen' fruits -

The 'dirty dozen' of the fruit and vegetable world are those most likely to soak up pesticides. Apples, strawberries, and grapes come out high on top of the list, so always try to buy organic versions of these fruits.

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Farmed beef -

Always go for grass-fed beef when you can. Studies have shown that antibiotics used in farmed beef can negatively affect human gut bacteria, and may lead to weight gain.

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Processed foods -

It's no secret that eating too many processed foods is bad news for the body. Metabolism-slowing bad guys like high fructose corn syrup and omega-6 fatty acids are found in abundance in processed foods, to keep them to a minimum. 

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Fried fast food -

Fried food from fast food restaurants is often high in trans fats, which could seriously slow down your metabolism. Research shows that a diet high in these fats could lead to abdominal obesity and weight gain.

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Frozen ready meals -

Those pre-prepared 'TV dinners' might be convenient, but they're unlikely to do your metabolism any favors. Check the ingredients—frozen dinners are often poor in nutrients and high in trans fats (which show up as hydrogenated oils), sugar, and sodium. 

Sources: (Runner's World) (Everyday Health) (Eat This, Not That!) (Healthline)

See also: Is there such a thing as "healthy sugar?"

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