Math for Grownups (27 page)

Take a look at the math. To lose 1 pound, you need to reduce your calorie intake by 3,500 (or burn an extra 3,500 calories a day). If you were to lose 7 pounds of fat in a week, you’d be reducing your calorie intake by an average of 3,500 calories every day. Now remember that an average man needs 2,500 calories a day and an average woman needs 2,000. Unless you’re consuming an extra 3,500 calories a day, you can’t reduce your calories by that much.

But could you burn that many calories a day? Sure, and here’s how: 7 hours of high-impact aerobics, 6 hours of mountain biking, 8 hours of golf (carrying your own clubs), or 13 hours of weight lifting. Oh, and those totals? They’re daily, not weekly.

So unless those pills are revving up your body, hummingbird-style, if you do lose 7 pounds in a week, it won’t be through loss of fat.

There simply is no quick or simple way to lose weight, unless you’re resorting to unhealthful methods. But there is an easy way to estimate your daily calorie intake. This method isn’t as exact as the formula presented earlier, but it works great for those who aren’t interested in precision.

To lose fat, eat 12 to 13 calories per pound of bodyweight

To maintain weight, eat 15 to 16 calories per pound of bodyweight

To gain fat, eat 18 to 19 calories per pound of bodyweight

If you weigh 155 pounds, here’s your calorie intake for each scenario:

Lose weight
→ 12 • 155 to 13 • 155—that is,
1,860 to 2,015—calories per day

Maintain weight
→ 15 • 155 to 16 • 155—that is,
2,325 to 2,480—calories per day

Gain weight
→ 18 • 155 to 19 • 155—that is,
2,790 to 2,945—calories per day

(Note that these guidelines are the same for men and women. The resulting calories per day might be on the high end for women and on the low end for men.)

Many nutritionists also recommend looking at an average daily calorie intake over a week. If you weigh 155 pounds and average 1,900 calories a day for a week, you’re likely to lose weight. If you average 2,800 calories a day for a week, the needle on the scale will probably move up.

A product’s nutrition label is made up of several distinct parts, and each part is designed to help you make good choices about what you’re eating. But which numbers are important, and why?

Michael’s doctor has warned him, “Watch your fat and sodium intake!” He’s also trying to lose a couple of pounds, so it won’t hurt to compare nutrition facts. And that’s exactly what Michael is doing. He loves soup, and he’s trying to decide between two brands.

First, Michael needs to make sure he’s comparing tomatoes with tomatoes, so he checks the serving sizes. One serving of Lovely Lentils is 1 cup, and one serving of Barley and Beef is 8 ounces. Are these equivalent? Yes. There are 8 ounces in 1 cup, so Michael (thankfully) doesn’t need to do any extra calculations.

Now he needs to consider the fat. What is the percent of calories derived from fat for each soup? To find this, he needs to divide the number of calories from fat by the total number of calories.

Lovely Lentils: 90
/
210
=
43%

Barley and Beef: 261
/
320
=
82%

Whoa! Barley and Beef’s percent of fat calories is twice as large as that for Lovely Lentils. There’s a clear winner here.

Still, Michael wants to look at the amount of sodium in each soup. Again, Lovely Lentils is on top, with a much smaller amount of sodium. And that brand is higher in vitamins A and B, calcium, and iron.

But there’s another reason why Michael should take a closer look at Lovely Lentils: the total calories. If he heats this soup up for lunch, he’ll eat fewer calories. Just what the doctor ordered.

Let’s say you want to eat that entire bag of chips at lunch. To balance that out—and not gain weight—you’ll have to move your body. There’s math involved there, too.

When your heart is working hard, so is your body. So, when you’re exercising, you should know how fast your heart is beating. Too close to normal, and you’re not exerting enough energy. Too fast, and you could be pushing it.

Your heart rate is measured in beats per minute. Calculating your heart rate is easy: Just find your pulse and count. You could count for an entire minute, but there is an easier way—start at 0 and then count for only 10 seconds. Now you have to do some math.

Let’s say that you counted 11 heartbeats in 10 seconds. How many heartbeats would you have in 1 minute? All you need to do is multiply by 6.

11 • 6
=
66

Why 6? Because there are 60 seconds in a minute, there are six 10-second periods in a minute. (Here’s another way to think of it:
60 / 10 = 6. And here’s another: 10 + 10 + 10 + 10 + 10 + 10 = 60.) So you need to multiply the number of times your heart beats during each 10-second period (which is 11) by 6.

This result is called your
resting heart rate
, or RHR. Another important number is your
maximum heart rate
, or MHR. This is the fastest your heart should beat, and it is not advisable for it to exceed that rate. You’re not necessarily going to keel over if your heart rate reaches its maximum. But you shouldn’t exercise for very long when your heart is beating that fast.

There are about half a dozen ways to calculate your maximum heart rate, and all of them come from highly respected experts. But for most folks, a simple formula works just fine:

MHR
= 220-
age

Let’s say that you’re 40 years old. In that case, your MHR should be 220 – 40 = 180 beats per minute.

Your RHR and MHR are the bases of the other heart rate zones. And your heart rate zones will help you exercise most efficiently. The American Council on Exercise defines these zones this way:

Take a look at the table. Should you simply take the percent of your resting heart rate to find how fast your heart should be beating during this kind of exercise? No, because that would put your rate during exercise at
less than
your RHR. That doesn’t make sense at all!

In fact, there is a formula you can use to find your target heart rate in each of these zones.

(
M
–
R
)
p
=
z

z
+
R
=
Z

M
is maximum heart rate

R
is resting heart rate

p
is the percent from the Intensity of Exercise table

z
is the zone

Z
is the zoned heart rate

Let’s take a look at an example.

Jesse is a competitive sprinter. In order stay on top of his game, he needs to monitor his heart rate during his daily workout. He’s 25 years old, and his RHR is 72 beats per minute (bpm). He has to use a formula to find his MHR:

MHR
=
220
–
age

MHR
=
220
–
25

MHR
=
195 bpm

Jesse’s trainer does the math and comes up with this:

• Jesse’s heart rate should not exceed 195 bpm at any time during his workout.

• When he’s warming up, his heart rate should be between 140 and 152 bpm.

• When he’s in his regular workout period, his rate should be between 152 and 177 bpm.

• And when he does short, intense bursts—such as sprints—his heart rate should be between 177 and 195 bpm.

Mazzy is tired of spending her mornings at the gym. She’d rather be snoozing in bed. Her trainer suggests
high-intensity interval training
(HIIT).

The idea is to switch up the intensity of your exercise—dramatically—which Mazzy’s trainer says will make her workout more efficient. The warm-up and cool-down are typical of most exercise routines. But in between, she’ll cycle through intense and easy exercise, forcing her heart and muscles to keep up with the sudden changes.

Here’s a sample workout:

• Slow walk (warm-up) for 3 minutes

• Fast run for 30 seconds

• Slow walk for 1 minute

• Fast run for 30 seconds

• Repeat previous “walk 1 minute, then run 30 seconds” set for 8 more cycles (9 cycles in all)

• Slow walk (cool down) for 3 minutes

Sounds great, but will Mazzy have time to sleep in and hit the gym before work? Or could she fit it into her lunch hour? Mazzy needs to know how long the workout takes.

Warm-up
=
3 minutes

Fast run
=
0.5 minute

Walk/run cycles
=
1.5 minutes • 9 cycles
=
13.5 minutes

Cool-down
=
3 minutes

Total
=
3
+
0.5
+
13.5
+
3
=
20 minutes

Mazzy can do it! She sets her alarm and hits the pillow happy.