Can you train your metabolism to work faster?
It’s the bugbear of many: you struggle to lose weight, but your friend cuts back for one day and the weight seemingly falls off or, even worse, they never have to moderate their diet to avoid weight gain.
Now, new research indicates that as individuals we metabolise some foods more quickly than others. This implies that if we knew more about how different foods affect our bodies, we could identify and avoid or cut back on our personal triggers for blood sugar spikes and excess energy. Sounds great right? But could reducing how much we eat of these foods affect the speed at which we lose weight as individuals?
We spoke to Professor Tim Spector, Dr Giles Yeo and nutritionist and personal trainer David Wiener to decipher the science.
What’s the science?
High levels of sugars or fats in the bloodstream can be caused by a sudden high intake of these nutrients, for instance when you eat a large piece of cake, or you have an inefficient (slow) metabolic response to eating a smaller piece of cake. This spike is associated with energy that is excess to requirements and therefore stored as fat.
Professor Spector’s study saw 1,100 participants (a mixture of identical and non-identical twins and unrelated individuals) fast overnight, then spend the following day in hospital. While there, their bloods were taken every half hour and they were given identical foods and portions. Their body’s response to the food was analysed. When they returned home for two weeks, they were given set foods and meals to eat, and they also ate their own food. Their responses were logged via wearable technology (glucose monitors) and an app, with further blood prick samples submitted. Their microbiome (gut bacteria) was also collected at the beginning and end of the study.
The result? “The metabolic response to food was so different between people in identical conditions. So, if they were given an identical muffin, for example, how much their sugar, insulin and blood fats went up varied about eight-fold between people. There was no average response. Even identical twins having the same meal at the same time had different responses”.
Combining all the data, they were able to create an algorithm and predict, with a 76 percent accuracy, how each participant would respond to any food.
What can you change about how you metabolise food?
In Professor Spector’s study, while one person had a fat or sugar spike after eating one type of food, another got the same response from a different type. So when you learn a friend lost two stone on a diet yet you struggled to lose a few pounds, it may be because they cut out ingredients that caused the spike for them but you’re still eating the ones that cause it for you – you’re metabolising the same food very differently. The time people ate also affected their response.
So in theory, if you knew what was causing your spike you could reduce your consumption of those ingredients and eat at times that best support the burning of your fuel efficiently. Of course, it’s important to make sure you’re getting all the nutrients you need from alternative foods, too.
Is Professor Spector confident in time we’ll be able to manipulate the speed at which we metabolise food via diet? “Yes, I think that we can already do it to some extent now”.
Basal metabolic rate (the rate at which we use energy while at rest to maintain vital functions such as breathing and keeping warm) is difficult to change. It’s caught up in our DNA, and we don’t yet know which genes impact it. It’s also difficult to measure.
“There is no way to train our basal metabolic rate with food to do anything because, given our genes, our metabolism is going to set to whatever it’s set at”, explains Dr Yeo.
You can adapt your diet so you’re eating less of the foods that cause these spikes (which is what Dr Spector has focused on), but you can’t change your basal metabolic rate so that regardless of what you eat everything will speed up.
If you believe your metabolic rate is slow, this is where it gets a bit depressing…
If you think someone who has a BMI in the ‘healthy range’ must have a faster metabolism than someone categorised as being ‘overweight’ or ‘obese’, and that if you lose weight your metabolism might pick up too, you’re wrong.
It’s true that if you have a larger build, Dr Yeo says it’s likely your metabolism will be higher than someone who has a slimmer build because “you have a bigger engine to run”. But here’s the kicker: if you lose weight your metabolic rate decreases.
“So, I’m 75kg”, says Dr Yeo. “Imagine I have a twin who used to be 85kg, but has lost 10kg so is now 75kg too. But I’ve never been 85kg. I will always be able to eat more than my twin... because he’s defending a higher weight than me.
“As you lose this weight, your brain hates it”, he continues, “because it considers it as reducing your likelihood of surviving. Keep in mind we’ve evolved from a time when there was not enough food. So whenever you lose weight a red flag goes off in your brain and two things happen: it makes you more hungry and it lowers your metabolism slightly to try and drag your weight back up.”
Dr Yeo says this will be the case whether you’ve reduced your weight gently over time or via an extreme diet.
“When you lose weight it doesn’t drop by that much, but you have to remember that 8 to 10 to 20 calories every single day, that kind of difference is enough to make a difference in 5 kilos of body weight over a few years.”
Are there magical ingredients that could speed up your metabolism, such as green tea? Dr Giles Yeo, Principal Research Associate at Cambridge University’s Metabolic Research Laboratories and MRC Metabolic Diseases Unit, says “No. There are some things that do increase your metabolism, but they’re mostly poisons”. Oh, perhaps we’ll leave them then.
Professor Spector is used to debunking myths and checks off 23 of them in his new book Spoon Fed. He agrees that when it comes to those magic ingredients, there’s little evidence.
But there is hope…
While you can’t speed up your basal metabolic rate with food, says Dr Yeo, there are a couple of ways you can change it: by increasing the amount of physical exercise you do and by building muscle mass.
“Anything from walking the dog to gardening and running is particularly effective at helping you maintain weight loss”, says the expert. He explains that doing exercise will temporarily raise your metabolic rate – basically for as long as you feel hot and sweaty afterwards.
As for increasing muscle mass, that becomes more critical as you get older and your metabolism drops further, although Dr Yeo highlights “I’m not suggesting we send Granny to the gym – just going for a gentle walk will help”.
David Wiener, nutritionist and personal trainer, says “in general, men tend to have a faster metabolism than women because they have more muscle mass, heavier bones and less body fat. But these are all factors that can be improved through exercise.
“Aerobic exercise is the best way to burn calories. You should aim for 150 minutes of this type of exercise every week, or 15-30 minutes every day. This includes running, walking, swimming and cycling. Alternatively, strength training is also a great way to burn calories”.
So what strength training exercises is the fitness expert a fan of? Burpees, mountain climbers, squat jumps and planks, though as with all new diet and exercise plans, you should speak to an expert before you embark on them.