New research shows our metabolisms have dropped since the 1980s. But these strategies will help you burn more calories all day long.
If there’s one dinner-table experience shared the world over, it’s enviously watching someone who is super-slim wolf down dessert with the explanation: “I have a really fast metabolism.” It’s surely among the most infuriating sentences in the English language for those of us more prone to the reverse, whose body’s apparently sluggish attitude to burning calories means a lifetime of staring wistfully into bakery windows.
So, what exactly is this mythical concept? Our metabolism, or basal metabolic rate, quantifies how many calories we need each day in order to survive. It’s an internal process that’s 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 an international study on metabolism patterns published in the journal Science indicates that the average metabolic rate declines during adolescence, before plateauing from the age of 20 until we’re 60. What that means in reality? According to the researchers’ calculations, the total energy expenditure in adults remains stagnant during these years, despite data suggesting this is the time we’re more physically active. It’s widely been assumed that our lazy modern lifestyles mean we move less, but the researchers found the opposite is true.
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We’re moving more than we were in the 1980s, thanks to the rapid rise of exercise as leisure, from weekend warriors smashing half marathons to middle-aged men in lycra, but yet we’re burning less. 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? 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 when they eat more saturated fat their metabolism speeds up, a finding that will now need to be repeated in humans. But in the meantime, should we up our fat intake to supercharge sluggish metabolic rates? Increasing our sat fat intake is, in a word, controversial. Too much of it from things like butter and meat spikes the risk of heart disease, though saturated fat from other dairy sources, like full-fat yoghurt and cheese, doesn’t seem to carry as great a risk, according to the latest research.
But going gangbusters on fat intake isn’t the only way to take charge of your metabolism. For those despairing that their DNA has doomed them to a 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 the amount of muscle and fat, there is about a 10 per cent variability in metabolic rate,” she says. Here are seven easy ways to harness yours. And go.
#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 Dr Michael Mosley, health guru and creator of The Fast 800 method. (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 to digest it”.
Essentially, the harder it has to work to break such foods down, the more calories it will burn in the process. One study found that high-protein products, such as eggs, chicken, lean red meat and fish, trigger a higher thermic effect of 20 to 30 per cent, compared with carbohydrates (five to 10 per cent) or fat (three per cent). More protein is also advisable the more candles we have on our birthday cake, as it helps maintain lean muscle. But before you go crazy, know this. Dr Saira Hameed, author of The Full Diet, advises there’s no need to eat it in abnormally high amounts. “We’re talking a two- not six-egg omelette,” she says. “But the metabolic advantage of this is protein is the macronutrient that most potently fires up metabolism.” Deliciously simple advice we can follow.
#2. Prioritise sleep
In news that will surprise no-one, sleep loss can hinder metabolism by triggering the body to store fat instead of burning it. A study published in Sleep Medicine found that among 5000 respondents, even one hour less shut-eye each night (than the recommended seven to eight) 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. The reason? Multiple studies have shown that poor sleep also leads to worse dietary decisions and reduced sensitivity to insulin, making you “metabolically groggy”, according to one paper from the University of Chicago.
Failure to process insulin correctly means more energy that enters the bloodstream will be stored as fat. Looking for food that will help boost the quality of your sleep? Pop a vitamin D supplement, down a glass of milk (it’s rich in tryptophan, an amino acid thought to have sedative effects), consume more magnesium-rich foods (think brown rice, pumpkin and spinach) and add more carbs like wholegrain pasta or brown rice to your evening meal.
#3. Do more 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,” explains Mosley. While moving more is not thought to affect this long term, burning more calories can certainly 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 boost your metabolism, but the jury is out,” says Roberts, noting that studies have indicated different results. While lifting “may not do much for metabolism in studies to date, keeping strong is important for overall health”.
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. The take home? Maintaining lean muscle may help you burn fat without even trying.
#4. Drink coffee or green tea
Chalk another one up for your daily espresso. According to a study published in The American Journal of Clinical Nutrition, 100mg per day of caffeine increased participants’ resting metabolic rate by three to four per cent; another, published in the British Medical Journal, suggested that high levels in the blood (via the likes of coffee or green tea) may curb body fat and type 2 diabetes risk. While among the more conclusive lifestyle factors when it comes to helping our metabolism along, Hameed warns “there’s a fine line between a metabolic rev-up and overdoing the caffeine because of its less positive health impacts, like speeding up your 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 so it’s out of your system before bed.
#5. Avoid crash diets
“It’s a cruel irony of weight loss that it gets harder as you lose weight,” says Chris van Tulleken, doctor and author of Ultra-Processed People. His take on this age-old dilemma? 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. The sobering proof? A 2016 study of participants in The Biggest Loser, the controversial reality TV program, revealed that while they may have dropped serious kilos, it had long-term implications. Researchers measured body weight, fat, metabolism and hormones at the end of the show, and again six years later.
What the clever folks in lab coats found? The contestants’ metabolisms had slowed significantly, and when they put weight back on, their metabolism didn’t bounce 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, with one contestant – who lost 108 kilos – regaining almost half of that, yet they were eating a hunger-inducing 800 calories a day. So, how can we lose weight but also prevent our metabolism from taking a nosedive? According to the Harvard School of Health, women shouldn’t drop below 1200 calories per day, with men staying at a minimum of 1500.
Many dietitians say not to cut intake by more than 200 to 300 cals daily. If you do need to diet, research suggests low-fat diets slow your metabolism the most. In a study in The New England Journal of Medicine, 21 people were put on 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 – their metabolic rate dropped by 95 calories a day, compared with 423 calories a day on the low-fat diet.
#6. Get tracking with new tech
Great news for lovers of all things tech-related: your metabolic rate can be measured and tracked via a range of devices, one being the Lumen – a handheld monitor that you breathe into in order to measure CO2 levels. Not dissimilar to an enlarged vape pen or USB stick, the nifty device reveals how many calories your body is 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 delivers tips on what you should eat and when, so that your body can easily switch between burning both fat and carbohydrates, rather than tucking them away into difficult-to-shift fat stores. In theory, this should make both weight loss and management easier – a major win for wellness-seekers looking to optimise their health, minus the constant yo-yo diets and restriction.
#7. Give your gut a fibre boost
Just like a virtual broom for your insides, eating more fibre is “an easy way to boost metabolism that’s 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 of this power macro 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. The other thing nutritionists confirm will make a major difference? Give ultra-processed foods (bacon, ice cream, white bread, we’re looking at you) a wide berth. Reason? They can disrupt the microbiome and insulin sensitivity, further messing with your metabolism.