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Question of the Week: What does "calories in vs. calories out" mean in terms of losing weight, and how does it help?

Posted Oct 28 2010 12:00am
First, it is important to know that one pound of fat is made up of roughly 3,500 calories. Therefore, in order to lose one pound of fat, you will need to burn 3,500 more calories than you take in. (Obviously not all in one day) 1-2 lbs is considered a safe amount of weight to lose each week. 1 pound doesn't seem like much to lose in a week, but think about it: you didn't gain 10 pounds in one week---noooo (although we have all felt like we gained 10 pounds in a week) it took a while to gain weight just like it is going to take a while to lose weight...be patient my friend...

Ok, let's work with losing one pound, or 3,500 calories per week 3,500 calories divided by 7 days (in a week) = 500 calories per day.

So, in order to lose 1 pound this week, you would need to burn 500 more calories each day than you consume. For example, if you eat 1500 calories a day, you need to burn 2000 calories a day in order to lose that pound you're working on. It sounds like a lot right? Not really--burning 2000 calories a day doesn't mean you have to spend 15 hours on a treadmill each day (phewww!) Our bodies are constantly burning calories all day long as part of our Basal Metabolic Rate (BMR). BMR is the amount of calories you burn while you are doing absolutely nothing...Why? Because it takes energy for the body to perform basic daily functions like breathing, circulating blood, digesting, and everything else that your good ole body does without you telling it to. BMR is different for everyone--based on age, gender and weight.

Here is a sample BMR for a woman: 1520 calories a day (we will use this number throughout the blog to demonstrate caloric needs)

Find out your BMR: http://health.discovery.com/centers/heart/basal/basal.html
Use your own BMR when you read the blog so you will have an idea of what your caloric needs would be!

Basically, there are 3 ways to create this 500 calorie/day defecit in order to lose 1 pound per week, and they all come down to burning more calories than you consume.

1. Eat fewer calories than you burn each day. (Without exercising)
To me, this one is the hardest one to do. Let's use the 1520 calories/day:

If your body burns 1520 calories/day and you want to lose a pound a week, then you would have
1520 calories/day
- 500 calories/day (because you need to eat 500 fewer calories than you burn each day to total 3,500 calories a week)
1020 calories/ day that you could eat and still lose weight.

See the problem? Any time you restrict your food intake to less than 1200 calories/day you should be under the close supervision of a Dr.... Not to mention, you would be staaarrrving! If you are not adding any physical activity to burn any extra calories than your 1520 calories/day, and you can only eat 1020 calorie/day to lose weight, it won't last- it is way to difficult (and not very healthy) to stick to a diet that low in calories for a long amount of time so chances are, you'll gain all of your weight back as soon as you go back to eating like a human again:) That is why physical activity is so important in losing weight and keeping it off- which brings us to the 2nd way to create a 500 calorie/day deficit.

2. Burn more calories than you consume by exercising.

That's it--there's the weight-loss secret everyone's been waiting for! Using 1520 calories/day again we see that if you eat all 1520 calories/day that your body needs to function and burn 500 calories/day at the gym, or park, or mowing the lawn (to each his own) then you have
1520 calories/day
+500 more calories that you burned with physical activity
2020 calories burned a day

See, your body is satisfied because it got the 1520 calories it needed that day, and it used them all to keep you alive, then it had to tap into your fat storage in order to find 500 more calories to use. So in total your body burned 2020 calories that day, 500 more calories than you so you created the 500 calorie deficit... keep up the hard work and you will lose 1 pound per week (500 calories a day x 7 days a week = 3,500 calories a week).

Not ready to jump head first into a 500 calorie burning workout? No problem; there's a "diet secret" for you too, and it just might be the most effective!

3. A combination! Eat fewer calories AND burn more calories by exercising.
This is considered the most effective way to lose weight and to keep it off because you combine diet and exercise. You don't have to starve all day or workout for 3 hours. Just find your balance!

Here we go again: 1520 calories/day

skip the 20oz Coca Cola and save 240 calories
+ 30 minute brisk walk burn about 270 calories
total calories saved/burned = 510 calories a day!

Keep in mind that you aren't burning 510 calories/day, you're only burning 270 calories so you would have to limit yourself to 1520 calories/day
- 240 calories (by not drinking coke, eating a cookie, etc...)
1280 calories that you could eat and still lose weight

If you eat all 1520 calories/day and only burn 270 calories on your 30 minute walk, then you only created a deficit of 270 calories/day-- which will still result in weightloss (0.5 pound per week- so it would then take you 2 weeks to lose 1 pound)
If you're feeling really good after your 30 minute walk, keep going! Burn baby burn!


**On a final note; for those of you who would like to maintain their current weight simply consume the calorie amount of your BMR...Your calories in should equal calories out. Remember though, that exercise is important in maintaining health not just for losing weight...The best part for you "weight maintainers"? If you burn 500 calories working out each day, you get to eat 500 extra calories (yummm!) because, remember, you want your calories to balance each other out.

Remember that 1520 calories/day is just an example, and is not appropriate for everyone.

Thanks to Marylin for submitting her question! I hope this helps!

Have a question for next Thursday's Question of the Week?
Ask the nutritionists Send questions to jrcarter@crimson.ua.edu , or cjchenault@crimson.ua.edu


*Don't forget about Trick or Treat for UNICEF!! Only 3 days left to provide clean water to 50 kids this Halloween!
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