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

Irish Examiner - Feelgood - - Health -

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.

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