MEASURING YOUR BODY FAT
Too much body fat and not enough muscle means your RMR is slower than it need be. It is possible to measure your body fat percentage, and many types of scales now do this for you using a technique called ‘bioelectrical impedence’. (Don’t worry – it doesn’t hurt!) A healthy range of body fat for adult women is between 24 and 34 per cent; for men it is 18 to 26 per cent. The lower you can get it, the higher your RMR should go. But beware: if a trainer in a gym asks if he or she can measure your body fat, they may employ a much more embarrassing method, involving the use of callipers to pinch the excess flab in your waist, thighs, hips and upper arms. This can be especially galling given that most trainers are god-like creatures with perfect abs, and you’d be perfectly entitled to run a mile from this ritual humiliation.
NATURE’S INJUSTICES
Women tend to burn fewer calories than men when doing the same exercise with the same effort because they have less muscle and more fat. Not fair, huh?
However, heavier people burn more calories doing the same exercise as thinner people, so a big, fat woman would burn more from a round of golf than a wee, skinny man.
Our RMR slows down naturally as we age. That’s why we tend to put weight on more easily in our thirties and forties and find it progressively harder to shift. It seems very unfair to have to put up with this alongside wrinkles, baldness and memory loss, but regular exercise should help in maintaining a healthy RMR.
Doctors have another method of measuring the fat in your belly by working out your waist-to-hip ratio (WHR). Researchers have found that it’s much more dangerous to have excess blubber in your middle than, say, on your hips and thighs, putting you at greater risk of heart attacks and diabetes, among other problems.
To see if you are at risk, measure your waist now at its narrowest point. Write the figure down before turning the page.
If you are female and your waist measures more than 35 in (86 cm), you are in the danger zone.
If you are a man with a waist of more than 40 in (102 cm), you need to slim down urgently. (Apart from anything else, your partner is going to have trouble getting their arms around you.) Now measure your hips at their widest point and divide your waist measurement by your hip measurement: waist ÷ hips = WHR. Write it down.
Women with a WHR of more than 0.85 are in trouble.
Men with a WHR of more than 1 are firmly in the ‘at risk’ category.
Shifting abdominal fat can be trickier than dealing with other kinds, but if you choose exercises that target it specifically (such as sit-ups or Pilates) you should see a difference after a while.
When you start a new fitness regime, it can be a good idea to take your measurements once a month and mark them on a chart on the bathroom wall so you can keep track of your progress.
(Make sure it’s not where guests can see it though, unless you want to give them a giggle.)
So, to increase your RMR, you need to replace your body fat with smooth, lean muscle and the way to do that is to become more active. One mega-workout a week is not the way forwards; it’s the steady, everyday type of activity that will make all the difference. We’ll look at the best types of exercise for boosting your metabolism in more detail on pages 32–7. But first, it’s worth looking at the amount of fuel you put into your body, via your mouth.
HOW MANY CALORIES DO YOU NEED?
There’s a complicated way of working out your calorie needs, and there’s also a simple formula. Let’s start with the more complicated way, by first working out your Resting Metabolic Rate, as follows:
If you are a woman around 20 years old, multiply your weight in kilograms × 24.2.
If you are a woman around 30 years old, multiply your weight in kilograms × 24.2 then subtract 2 per cent.
For each subsequent decade, subtract another 2 per cent. So, a woman of 40 weighing 70 kilos will make the following calculation: 70 × 24.2 = 1,694 1694 – 2% = 1,660.12 1660.12 – 2% = 1,628.92 Her RMR is 1,628.92
If you are a man around 20 years old, multiply your weight in kilos by 26.4. Then subtract 2 per cent for each subsequent decade.
So, we’ve now established that our 40-year-old woman would burn 1,628.92 kcal a day while doing no exercise at all. But hang on a minute – it does get a little more complicated …
As well as through our RMR, we also burn calories through something called the ‘thermic effect of food’, again – and you’ll like this – requiring no effort at all. This means that when you eat a Danish pastry containing 411 kcal, for example, 10 per cent of these (i.e. 41.1 kcal) are burned in the sheer effort of digestion – leaving only 369.9 kcal to be stored in your hips. Interestingly, some claim that a celery stick uses more calories when being digested than it contains, making it a useful little weight-loss tool (shame it’s so boring to eat).
So, going back to our 40-year-old woman: she would so far have burned 1,628.92 kcal plus another 10 per cent of the total number of calories she eats in the day. But there’s still something else to take into consideration …
The other way in which you burn calories – and the one over which you have most control – is known as the ‘thermic effect of exercise’. This doesn’t just apply to formal exercise sessions, like going to the gym, running in the park or swimming. Every single movement your body makes calls for muscles to contract in some way and that requires energy – although the calories burned while updating your Facebook profile are negligible when compared with those burned running a marathon. In a lazy person the thermic effect of exercise might account for just 10 per cent of the calories burned but in an Olympic athlete, it could be up to 50 per cent.
So the 40-year-old woman we’ve been looking at will burn 1,628.92 kcal plus 10 per cent of her calorie intake, plus all the calories she burns daily through exercise/activity. The resulting figure represents the number of calories she can eat in a day without losing or gaining weight. It’s tricky, isn’t it? There’s a brief summary in the box at the bottom of page 26.
[Your weight in kg × 24.2 – 2% for each decade over 20] – [calories consumed in a day × 10%] – calories burned through activity in a day = no. of kcal you can eat in a day if you want to keep your weight stable
Now let’s look at the simpler formula for calculating the number of calories you can eat in a day without putting on weight:
If you are female with a lifestyle involving mainly sitting on your butt (you drive everywhere, have a desk job and think exercise is a four-letter word), multiply your weight in kilos by 26.
If you are the male equivalent of the lazy woman above, multiply your weight in kilos by 31.
If you are female and tend to be on your feet doing some kind of physical activity (walking, housework, mowing the lawn, etc.) for at least an hour a day and you take proper exercise (running, gym, sport) three times a week, multiply your weight in kilos by 33.
If you are the male equivalent of the moderately active woman above, multiply your weight by 37.
If you are a super-fit woman who gets an hour of moderate activity a day and five or six sessions of proper exercise (that makes you out of breath) a week, multiply your weight in kilos by 39.
If you are the male equivalent of the super-fit woman above, multiply by 44.
WHERE DO YOU GO FROM HERE?
Now you know how many calories you