BE­HIND THE HEAD­LINES WITH DR TIM CROWE

The net is full of health myths — but how much is true? Lets start with five!

Healthy Food Guide (Australia) - - CONTENTS - Dr Tim Crowe is an Ad­vanced Ac­cred­ited Prac­tis­ing Di­eti­tian and nutri­tion re­search sci­en­tist. Con­nect with him at think­ingnu­tri­tion.com.au

Sugar makes kids’ be­hav­iour hy­per­ac­tive

THE SHORT AN­SWER It’s not the sugar at the party — it’s the party!

The sugar and hy­per­ac­tiv­ity link is one of the most pop­u­lar food-be­hav­iour myths do­ing the rounds. Yet sci­ence has firmly busted this fa­ble, with dozens of stud­ies fail­ing to find any link. When par­ents are un­aware if their child has been given sugar or a non-sugar sub­sti­tute, they can’t recog­nise any dif­fer­ence in their child’s be­hav­iour. It’s only when they be­lieve their child has had a sug­ary drink, even though the drink con­tains no sugar, that they rate their off­spring’s be­hav­iour as more hy­per­ac­tive.

So, why do kids seem so hy­per­ac­tive when they eat a lot of sugar? It all comes down to the con­text within which they eat it. When kids are hav­ing fun at birth­day par­ties, sugar-laden food is of­ten served. The fun, free­dom and con­tact with other kids makes chil­dren hy­per­ac­tive, not the food they eat.

Mi­crowav­ing veg­eta­bles de­stroys their nu­tri­ents

THE SHORT AN­SWER We should worry less about nutri­ent loss and more about eat­ing more ve­g­ies.

Mi­crowav­ing your food has no more ef­fect on the nu­tri­ents in that food than any other way of heat­ing it. Heat does cause a small drop in some nu­tri­ents such as fo­late, vi­ta­min C and thi­amin — but this can never be avoided, no mat­ter how you cook your food.

Cook­ing in a mi­crowave has its ad­van­tages. The shorter cook­ing time means there’s less time for heat to af­fect sen­si­tive nu­tri­ents. And as a bonus, with lit­tle wa­ter needed, there are min­i­mal losses caused by nu­tri­ents leech­ing into the cook­ing wa­ter.

A slow me­tab­o­lism is to blame for weight gain

THE SHORT AN­SWER It’s pos­si­ble, but not usu­ally the sole rea­son.

It’s easy to lay all the blame for weight gain on a ‘slug­gish me­tab­o­lism’. The re­al­ity is that your rest­ing me­tab­o­lism, which is the num­ber of kilo­joules your body uses at rest, in­creases rather than de­creases as your weight goes up. The ex­tra en­ergy then helps sup­port the greater vol­ume of your body and the mus­cle needed to carry the ex­tra weight.

Only in cer­tain rare sit­u­a­tions where a per­son may have an un­der­ly­ing med­i­cal con­di­tion, such as an un­der­ac­tive thy­roid gland, could weight gain be ex­plained by a ‘slow me­tab­o­lism’.

Cel­ery & let­tuce burn more calo­ries than you con­sume

THE SHORT AN­SWER There’s no such thing as a ‘neg­a­tive-calo­rie’ food — it’s a nu­tri­tional uni­corn.

Even the hum­ble stick of cel­ery, while made up of about 95 per cent wa­ter, still con­tains a small num­ber of kilo­joules — 65kJ (16cal) to be ex­act. There is an en­ergy cost in di­gest­ing food, but it only adds up to about 10 per cent of the kilo­joules in the food. So even cel­ery adds some kilo­joules to your diet. It’s a small, but not neg­a­tive, num­ber.

Foods like cel­ery, let­tuce and broc­coli can help you lose weight, partly be­cause if your mouth is full of veg­eta­bles, there’s a lot less room for high-kilojoule foods like cakes and chips.

You need to ex­er­cise in the ‘fat­burn­ing zone’

THE SHORT AN­SWER You may burn fat, but you need to ex­er­cise longer.

The fat-burn­ing zone is a con­cept that the body burns a greater amount of fat dur­ing lower-in­ten­sity aer­o­bic ex­er­cise than it does dur­ing higher in­ten­si­ties. It is true that the body burns off the great­est per­cent­age of fat at lower lev­els of aer­o­bic ex­er­cise. How­ever, it is also true that dur­ing higher in­ten­si­ties you burn far more to­tal kilo­joules, and more fat kilo­joules over­all.

Low-in­ten­sity ex­er­cise does help with fat loss, but you just have to do it for a longer time. Short on time? Then it makes sense for you to work as hard as you can for a shorter pe­riod of time. The best ex­er­cise for you is the sort that you en­joy, be­cause it’s some­thing you will stick at in the long term.

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