Exercise: How Much is Enough?

We’ve all heard recommendations for exercise, but then we try it and we don’t see the results we want. So how much exercise is enough?

Let’s talk about money for a minute. Just like exercise, we talk about saving for retirement.  But the reality is, by the time we get to the end of the month, we have $5 left, and it hardly seems worthwhile to put that in savings.  $5 a month isn’t going to get us a retirement nest egg of a million dollars, but it might be enough for a nice vacation, or the down payment on a car.  If I want to have enough for retirement, I might have to cancel my cable and drive an old car for awhile in order to save a significant amount of money.  Significant savings require significant sacrifice.

Say we did put $10 a month away. Every month. And every year we earned a measly 5% interest on it every year.  At the end of 10 years, we’d have $1575.  That might not be enough to retire on, but it would keep me from having to put the car repair on my credit card.  It’s a start, and it’s certainly better than nothing.

Back to exercise.  What are the benefits of exercise?  Improved sleep. Better sexual function, Decreased risk of diabetes and obesity. Bone strength. Decreased risk of depression, heart disease and stroke. Decreased risk of many cancers, and improved survival from the bad ones. Less back pain. Almost all the studies that document these benefits use 150 minutes of brisk exercise “most days” as their measure.  That’s right: 30 minutes a day, 5 days a week.  Not a huge sacrifice, but if you’re not there yet, don’t despair- just start today with five minutes.

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But now you say you want to lose weight.  (Remember: moderate exercise leading to a 5-7% weight loss over 4 months decreases your diabetes risk by 58%.  That’s right: for a 200lb woman, a 10lb-weight loss is enough to cut your DM risk in half!)  How much do you have to exercise for that?

On average, walking 1 mile burns 100 more calories than you’d burn sitting. Not a perfect calculation, but it will do for our purposes.  So say in the morning, I get up and walk 2 miles in 30 minutes.  I burned about 200 calories more than I would have otherwise, and then I have a Pepsi because I feel good about walking in the morning.  My 1 can of Pepsi is 150 calories.  So what is my net burn? Only 50 calories.

To lose one pound, I have to burn 3500 extra calories over what I took in.  In a week, that’s 500 calories a day to lose 1 pound in a week—and that’s without replacing my calorie-burn with extra food or drink calories.

Those extra calories often are hidden in beverages, or portion sizes.  For example, a Quarter Pounder with Cheese, large fries and a large soda is 1,380 calories.  Or: a 13 mile walk.  If I have a regular cheeseburger, small fries and a water: 540 calories, or a 5-mile walk.

If it takes you 30 minutes to walk around the 1 mile park, I say “Good for you!”  You are outside, getting vitamin D and doing enough walking to decrease your risk of many cancers, stroke, heart disease, depression, sexual dysfunction and insomnia.  As you do it every day, little by little it will be easier, and in that 30 minutes, you will cover 2 miles. That brisk walk is enough to reduce your risk of diabetes.

But if you want to lose weight, you can’t expect exercise to do the whole job. If you’re currently gaining a pound every week or two, it means your current intake is 3500 calories more each week than you are currently burning.  If you’re eating three large meals and snacks and sweetened beverages, a 30 minute walk isn’t going to bring your weight down.  But if you start cooking smaller meals at home, snacking on fruit only, drinking water instead of sweetened drinks, and walking 3 miles a day twice a day, you’re going to lose weight. Slowly, sensibly, and in a way that will be sustainable over the long term.

Let’s talk for a minute about the dreaded weight loss plateau.  What’s going on?  You’ve changed your diet, been exercising and have lost 40 pounds, but now you’re stuck.  The weight just won’t come off any more.  Two things have likely happened. First, you weigh less now, so the number of calories you expend sitting, sleeping and walking is less.  That 2-mile walk burns 50 fewer calories for the same amount of walking when you were 40lbs heavier.

Second, your body has become more efficient.  Two miles used to wipe you out: you were sweating and exhausted at the end. Now you feel energized and invigorated by a two mile walk.  The solution? Cut a few more calories (leave the top piece of bread off your sandwich, maybe?) and add a few more miles to your daily walk. Change it up: add pool walking once a week, or an exercise bike for half an hour.  Doing a different kind of exercise will feel hard and use different muscles, thus increasing your calorie expenditure.

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If you put your $10 away for 10 years and then start drawing money out of your account little by little, what happens? Your balance dwindles. It’s math.  Losing weight is a lot of math, too: energy out must be greater than energy (food) in if you want to lose weight.

But if you want to live a longer, fuller, healthier, happier life, a brisk 30 minute walk every day should do the trick.

Click to read more on the other benefits of exercise, or what you can do to decrease your risk of diabetes.  Next month I’ll post on sleep: more than zzzzs.

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