Seven easy ways to fire up your metabolism

New research shows our metabolisms have dropped since the 1980s. But these strategies will help you burn more calories all day long. Photo / Getty Images

If there’s one dinner-table experience shared the world over, it’s enviously watching someone super-slim wolf down dessert with the explanation: “I have a really fast metabolism.” It is surely among the most infuriating sentences in the English language for those more prone to the reverse, whose body’s apparently sluggish attitude to burning calories means a lifetime of staring wistfully into bakery windows.

Our metabolism or basal metabolic rate quantifies how many calories we need each day in order to survive. It is an internal process running 24/7, turning what we eat into energy and governing everything from our circulation to breathing and cell repair.

Metabolic speed is mostly a matter of genetics, with age, weight and height being the main determinants. The heavier you are the more calories you burn, but since lean muscle tissue burns more calories than fat, two people of exactly the same weight may have very different processing speeds.

But now new research from the University of Aberdeen and the Chinese Academy of Sciences in Beijing has shown that over the past 40 years, average metabolic rates have plummeted.

According to the researchers’ calculations women are burning 122 fewer calories and men are burning 220 fewer than they were in the 1980s, despite us moving more than we were then. It has widely been assumed that our lazy modern lifestyles mean we move less, but the researchers found the opposite is true. We’re moving more than we were in the 1980s, probably due to the trend towards exercising in our leisure time.

Increasing our saturated fat intake is controversial. Photo / 123RF

Experts say this fall in our energy expenditure when our bodies are at rest (also known as our metabolic rate) could be a contributing factor in the growing obesity epidemic.

One explanation given by the scientists was the way that our diets have changed. We now eat less meat and dairy, due to the advice to cut saturated fats, and more ultra-processed carbohydrates, such as frozen pizzas and ready meals.

Studies in mice have shown that when they eat more saturated fat their metabolism slows, a finding that will now need to be repeated in humans. But in the meantime should we up our fat intake to increase our sluggish metabolic rates?

Increasing our saturated fat intake is controversial. Too much saturated fat from butter and meat increases the risk of heart disease, though saturated fat from other dairy sources like full-fat yogurt and cheese does not seem to carry as great a risk, according to the latest research.

But increasing your fat intake isn’t the only way to take charge of your metabolism. For those despairing that their DNA has doomed them to slow calorie burn, we do have some say in the matter, says Susan B Roberts, professor of nutrition at Tufts University in Boston and founder of theidiet.com. “Once you account for body weight, age and amount of muscle and fat there is about a 10 per cent variability in metabolic rate,” she says.

Here are seven ways to harness yours.

1. Eat more eggs

“There is some evidence that consuming more protein can help to boost your metabolic rate by something called the thermic effect of food,” says Michael Mosley, creator of thefast800.com. (The thermic effect is how much energy it takes your body to digest, absorb and metabolise what you consume.) Protein is key “because your body uses up more energy by digesting it”.

You may be able to boost your metabolic rate by eating more eggs. Photo / Getty Images

Essentially the harder it has to work to break such foods down, the more calories it will burn in the process. One 2004 study found that high protein products, such as eggs, chicken, lean red meat and fish, trigger a higher thermic effect of 20-30 per cent, compared with carbohydrates (5-10 per cent) or fat (0-3 per cent). More protein is also advisable as we get older as it helps maintain our muscles.

Saira Hameed, consultant endocrinologist at Imperial College Healthcare NHS Trust and author of The Full Diet, says, there’s no need to eat it in abnormally high amounts. “We’re talking a two- not six-egg omelette,” Hameed says. “But the metabolic advantage of this is that protein is the macronutrient that most potently fires up metabolism.”

2. Prioritise sleep

Sleep loss can hinder metabolism by triggering the body to store fat instead of burning it. A study published in Sleep Medicine last month found that among over 5,000 respondents, even one hour less shut-eye each night (than the recommended seven to eight hours) was linked to a 12g increase of visceral fat – the kind that lines the organs, raising the risk of metabolic conditions such as diabetes and heart disease.

Multiple studies have shown that poor sleep also leads to worse dietary decisions, and reduced sensitivity to insulin, making you “metabolically groggy”, according to a paper from the University of Chicago. Failure to process insulin correctly means more energy that enters the bloodstream will be stored as fat.

3. Do squats

While you can’t exercise off a bad diet, upping your calorie burn certainly helps. “Exercise, at least in the short term, can raise your metabolic rate,” Mosley explains. While moving more is not thought to affect this long term, burning more calories can help keep weight gain at bay.

But what about building up our muscles to increase our metabolic rate long-term? “It’s widely assumed that strength training will increase metabolism. The jury is definitely out,” Roberts says, noting that studies have indicated different results. While lifting “may not do much for metabolism in studies to date, keeping strong is important for health in old age”.

Experts recommend regular resistance training such as squats and press-ups, to maintain muscle mass as we age, a process that might account for the drop off in metabolism after the age of 60. Maintaining lean muscles will help maintain your metabolic rate.

According to the US National Council on Strength and Fitness, 6kcals are burnt per pound of lean muscle daily, compared with 2-3kcals daily per pound of regular mass, so it makes sense to maintain your muscle mass.

4. Drink coffee or green tea

According to a study published in The American Journal of Clinical Nutrition, 100mg per day of caffeine increased participants’ resting metabolic rate by 3-4 per cent; another, published in the British Medical Journal last month, suggested that high levels in the blood (via the likes of coffee or green tea) may curb body fat, and type 2 diabetes risk.

100mg per day of caffeine increased participants’ resting metabolic rate by 3-4 per cent. Photo / 123RF

While among the more conclusive lifestyle factors when it comes to helping our metabolism along, Hameed warns that “there’s a fine line between a metabolic rev up and overdoing the caffeine because of its less positive health impacts, like speeding up the heart rate or making it difficult to fall asleep”. So what’s the caffeine sweet spot? Drink two or three cups a day, but stop at noon to make sure it’s out of your system before bed.

5. Avoid crash diets

“It is a cruel irony of weight loss is that it gets harder as you lose weight,” says Chris van Tulleken, doctor and author of Ultra-Processed People. He believes that “weight is the only variable” under our control, when it comes to the major determinants of our metabolic rate – but, perhaps yet more cruel, is the fact that if you have gone on a diet, your metabolism may adjust to the reduced calories and upped exercise regime.

A 2016 study of participants in The Biggest Loser, a reality TV weight-loss programme, found that six years after their involvement their metabolism slowed down. Researchers measured body weight, fat, metabolism and hormones at the end of the programme, and again six years later.

The research showed their metabolisms had slowed significantly, and when they put weight back on, their metabolism didn’t go back to previous levels. Those who had maintained a lower weight once the show ended had to do so by sticking to a significantly reduced diet, the study found, with one contestant – who lost 17st– regaining almost half of that, yet they were only eating 800 calories daily.

A 2022 “reinterpretation” of the results, published by one of the original study’s researchers, suggested that the metabolic slowing was so great among contestants due to weight loss being the result of lengthy, sustained periods of physical activity, but added that further “longitudinal” studies were needed.

“It is a cruel irony of weight loss is that it gets harder as you lose weight,” says Chris van Tulleken. Photo / Getty Images

So how can we lose weight but also prevent our metabolism from taking a nosedive? Harvard Public School of Health says women shouldn’t drop below 1200 calories per day and men should not drop below 1500. Many dietitians say not to cut intake by more than 200-300 calories daily.

If you do need to diet, research suggests low-fat diets slow your metabolism the most. In a 2012 study in The New England Journal of Medicine, 21 people were put on both a low-fat diet and then a high-fat ketogenic diet. Both diets resulted in a drop in metabolic rate, but the keto diet was far less damaging. On the ketogenic diet, their metabolic rate dropped by 95 calories a day, compared with 423 calories a day on the low-fat diet.

6. Give your gut a fibre boost

Eating more fibre is “an easy way to boost metabolism that is not generally known”, says Roberts, who co-authored a paper on its benefits in 2017. “Any and all foods with fibre are good,” she adds, such as “green veggies, [and] legumes like chickpeas. Also high fibre cereals (such as muesli or bran), which are an easy source of fibre that you don’t need to cook.”

The benefits are thought to come from fibre upping the production of short-chain fatty acids in the gut microbiome, and slowing the rate at which food is absorbed. You might also want to give ultra-processed foods a wide berth as they can disrupt the microbiome, increase and reduce insulin sensitivity, further messing with your metabolism.

7. Get tracking

Your metabolic rate can be measured and tracked via a range of devices, such as Lumen – a handheld monitor that you breathe into in order to measure your CO2 levels. Not dissimilar to an enlarged vape pen or USB stick, it tells you how many calories you are burning and tracks whether you’re burning mostly carbs (high CO2 in the breath) or mostly fat (low CO2 levels), and is controlled via a smartphone app.

Lumen’s chief aim for “hacking your metabolism” is flexibility. The device gives you tips on what to eat and when, so that your body can easily switch between burning both fat and carbs, rather than tucking them away into difficult-to-shift fat stores. In theory, this should make both weight management and loss easier.