Wednesday, March 16, 2011

Weight Loss, Anyone?

Department of repurposing: I took a final in my Sports Nutrition class this week. It was four questions outlining hypothetical scenarios in fitness and nutrition. Despite staying up until 3 a.m. two nights in a row to complete the assignment, I thought it came out okay, so I decided to share with you.

Question #1 asked us to use our knowledge of exercise physiology and nutrition to give advice to a weight loss group about how exercise impacts weight loss.

Good afternoon. If you want to make lasting changes in your weight and body fat levels, there a few things you need to know.

One pound of body fat contains around 3,500 Calories. Calories are a measure of energy, and because, according to the laws of physics, energy can't be created or destroyed, the Calories you ingest as food must be burned off by activity or they will be stored as fat. Conversely, if you ingest fewer Calories than you expend in your activities, you will lose weight.

If you create a Calorie deficit of about 1,000 calories per day, you will lose two pounds per week, which experts consider a safe and sustainable rate of weight loss. This is best done by a combination of reducing Calories by 500 per day and increasing activity levels by 500 per day. This is because merely cutting Calories without exercise can lead to a loss of lean body mass along with fat.

When you are planning an exercise program, you must take into account four factors: how you will exercise (mode), how hard you will exercise (intensity), how long you will exercise (duration), and how often you will exercise (frequency). For weight loss and maintaining weight loss, the American College of Sports Medicine (ACSM) recommends at least 250 minutes per week (frequency and duration) of moderate-intensity (intensity) aerobic (mode) exercise. This means at least 50 minutes of moderate exercise most days of the week.

Moderate exercise (as contrasted with vigorous exercise) is recommended for weight loss for a couple of reasons. Although you can burn more Calories per minute with high-intensity exercise, you cannot exercise for as long at high intensity as you can at moderate intensity. And according to Melvin Williams in Nutrition for Health, Fitness, & Sport, duration is more important for weight loss. In addition, high intensity exercise is more correlated with injury, and if you become injured, you might derail your exercise plan. And finally, high intensity exercise can be hard and unpleasant for many people. If your exercise does not hurt, you are more likely to stick with it for the long term—and reap the benefits of weight loss.

By the same token, do not be taken in by the myth that low intensity exercise “burns more fat” and is therefore better for weight loss. Expressed as a proportion of total Calories burned, yes a higher percentage of fat Calories are burned in low-intensity exercise. But what is important for weight loss is the total number of calories burned. And low-intensity exercise just does not burn enough Calories to be worth your while—unless you have lots and lots of time.

What is moderate exercise? Willams notes that moderate aerobic exercise is exercise that burns between 5 and 10 Calories per minute, depending on your body weight. It includes activities such as jogging at 5 MPH, cycling at 10 MPH, swimming at 30 to 40 yards per minute, and walking briskly at 3 to 4.5 MPH. If you carry your own clubs, it can even include golf.

Although aerobic exercise is key for weight loss, incorporating a resistance training program alongside your aerobic exercise can be very beneficial. Resistance training can help you change your body composition. The muscle you add while weight training is metabolically active tissue that burns Calories even at rest. Fat is not metabolically active. In addition, resistance training while cutting Calories can help you hold onto the muscle you might otherwise lose while dieting.

Finally, you can burn Calories outside of exercise by increasing your daily physical activity: Take the stairs, get off the bus a stop or two early, park on the outer fringes of the parking lot, do a set of crunches or push-ups during t.v. commercials instead of getting a snack.

In any exercise program you should start slowly to build up your endurance and avoid injury. You should set realistic goals and track your progress. You should strive to prioritize exercise so it doesn't get lost amid the other demands of a busy life. And, maybe most importantly, it's good to try to make exercise as pleasurable as possible. You want to enjoy it both so that you will exercise for longer each day and so that you can adopt exercise for your whole life.


Sarah S said...

Good thorough advice! But what if a person (aka me) only wants to commit to 250 minutes of low intensity exercise a week? Will the weight come off, but just slower? Would you recommend halving the goal (e.g. 1 lb a week and only reducing calories by 250 a day?). Or will it just not cut the mustard?

Miriam said...

Anything is better than nothing! I'm curious as to why you only want to do low intensity--and also what low-intensity means to you. I think you could get away with low intensity exercise, but I think you'd have to cut MORE calories per day rather than fewer to lose even a pound per week, since low intensity exercise does burn a lot fewer calories. Don't forget, low-intensity exercise does bring health benefits (although not as many as moderate intensity), so if that is your goal, you're good to go with low-intensity.

Miriam said...

Also, I just posted another presentation I gave earlier this year that includes a another rant about low-intensity exercise. Don't think it's in reaction to your comment--I'm just looking over the work I've done this quarter and posting some of it.

Sarah S said...

Well, I walk to work when I can - I try and do it at least one way per day, sometimes twice, although sometimes none, depending on weather. It's about 2 miles door to door. I don't rush it, as I don't really enjoy walking fast and also I don't want to show up to work all sweaty. It's a form of exercise I like and can commit to long term (like, for the rest of my life, as opposed to running ). I don't want to commit any more time to exercise, except maybe a few hours of hula hooping on Sundays, and the occasional walk/park/swim with my kid. Just wondering if I would ever lose weight that way, or if as you said, a breath mint (or, ahem, chocolate) would just undo it all in a second.

Erick Flaig said...

The only diet plan that works, in the end, is so old it was written on a rock: Don't eat so much.

Good post!

Miriam said...

Well, Sarah, I just ran numbers based on a 15-minutes-per-mile pace (does it take you around a half hour to get to work?) If so, each time you walk to work or home you burn about 160 calories. So if you wanted to lose about a pound per week, you would have to cut about 340 calories per day from your diet. Not impossible by any means. But keep in mind that burning more calories per day correlates more closely with weight loss and weight maintenance.

Sarah S said...

I certainly do not walk a 15 minute mile! I like to take it real easy - I'd say closer to a 25 minute mile.