Vital to keep your inner engine in good working order
Metabolism has a bad rep when it comes to weight loss, but is it the enemy we make it out to be? Liz Connor asks some experts to explain
YOU’RE eating a balanced, nutrient-rich diet, you’re regularly working up a sweat in your local spin studio, and you’ve put a virtuous ban on all after-work wines at the pub. So when you step on the scales after weeks of blood, sweat and tears, why has your weight-loss progress stubbornly plateaued?
Chances are you’ll have heard someone blame their slow metabolism for their weight-loss struggles at some point. The general idea is that if you’ve been blessed with an overactive or fast one, you can eat more, work out less, and still maintain a svelte figure.
But what exactly is the mythical M word, how does it work, and can it really be the reason why some people find it harder to lose weight than others? We asked some experts to weigh in...
Metabolism in a nutshell
Metabolism is an umbrella term that’s used to describe lots of different metabolic reactions that occur in the body, whose job it is to keep you alive (it’s about way more than just controlling weight and body fat).
“These reactions do a variety of things, like generate energy, regulate growth, repair and general body maintenance,” explains GP Sarah Brewer.
Think of it like the engine that keeps your body running. If you laid in bed all day and didn’t move a muscle, the calories you’d burn just from staying alive would be what’s known as your basal metabolic rate.
Generally speaking, the speed of your metabolism is judged on the number of calories you burn in a given amount of time. On top of your basal rate, how fast your internal engine runs is based on how many calories it takes to digest and process food, undertake exercise and perform activities like fidgeting, changing posture, standing and walking.
It’s as simple as this: The faster your metabolism, the more calories your body needs. This is the reason some people can eat a lot without gaining weight, while others seem to need less to accumulate fat.
So why do some people have a faster metabolism than others?
“The rate at which you burn calories depends on many factors, including your age, gender, hormone balance, level of physical activity and your diet and lifestyle,” says Dr Brewer. “It also depends on your weight and, in general, the more you weigh, the higher your resting metabolic rate.”
Brewer explains that your metabolism is also partly regulated by the thyroid gland, which produces two iodine-containing hormones, thyroxine and triiodothyronine. These hormones enter cells and switch on genes that boost the burning of glucose, fat and protein to generate energy. If you have an underactive thyroid gland, low levels of these hormones can cause your resting metabolic rate to slow by as much as 40%, so you’ll gain weight more easily. Your metabolic rate also depends on your lean body-mass percentage, as muscle burns more energy than fat, and it’s also affected by your level of physical activity.
“Even your diet and lifestyle play a part too,” says Brewer.
She explains that eating protein-based foods, for example, uses up more energy and generates more heat during processing than eating fat and carbohydrates.
“This effect, known as ‘dietary-induced thermogenesis’, can account for 10% or more of the energy provided by foods - especially protein-rich foods.”
How does age affect your metabolism?
Evidence seems to suggest that, generally speaking, the metabolism slows down as we get older, which may be why some people suddenly find it harder to keep extra weight off (but of course, this isn’t the case for everyone).
“The most significant change is loss of lean muscle tissue, which is mostly replaced with fat. This process, known as ‘sarcopenia’, will occur naturally unless you continue to follow a muscle-building regime and obtain sufficient protein in your diet to build new muscle,” says Brewer.
“Resting metabolism also slows by around 5% every 10 years after age 25 and as a result, your daily need for calories goes down.”
Is your metabolism to blame?
When it comes to weight, metabolism is important, and while some believe that genetics play a part in its speed, it’s still an area that needs further research.
“In a sense, your metabolism may play a small part in whether you lose or put on weight,” says Dr Will Hawkins, a nutritionist. “However, the main contributor to weight-loss or gain is always how many calories your eating vs how many calories you’re expending.”
If you’re looking to lose weight this autumn, Hawkins believes the best way to see results is to make sure you balance the calories you take in against the calories you burn up through good old-fashioned exercise.
KEEPING TIME: The faster your metabolism, the more calories you need, but it slows as you age which in turn reduces the number of calories you need in a day.