Thursday, October 20, 2005

The New Math of Weight Loss

Ahhh, I love it when researchers publish data that highlights the flaws in the calorie theory and then they conveniently revert to the use of statistics to avoid the obvious!

Want to see the latest shenanigans with statistics?

Check out the data presented at the North American Association for the Study of Obesity (NAASO) conference this past weekend - as reported by Fox News in their online article, "How Much Exercise Sparks Weight Loss?" - presented by Dr. John Jakicic, a Professor of Health and Physical Activity at the University of Pittsburgh.

For two years, Dr. Jakicic has followed more than 200-obese women (average age 37, average BMI 32 at the start) on a calorie-restricted diet and varying exercise routines:
  • average calorie intake = 1,200 - 1,500 calories per day
  • Fat intake restricted to 20-30% of calories
  • moderate amount/moderate intensity
  • moderate amount/vigorous intensity
  • longer amount/moderate intensity
  • longer amount/vigorous intensity
  • those following the "moderate" regiments burned about 1,000 calories per week from exercise
  • those following the "longer" regiments burned about 2,000 calories per week from exercise

Now the findings were interesting, body fat percentage lost:

  • longer amount/vigorous intensity = 7.2%
  • longer amount/moderate intensity = 6.5%
  • moderate amount/moderate intensity = 4.9%
  • moderate amount/vigorous intensity =3.7%

But, what's wrong with this picture?

After two years these women only managed to lose between 3.7% and 7.2% of their body fat? How is that even possible given the calorie restriction and calories burned in exercise?

It's not!

If the calorie theory is applied, these women should have lost a lot more weight over two years.

Forget the statistics - Just do the math!

We know the average age was 37....we know the average BMI was 32....let's assign a height of 5'7" as our baseline here, which means a body weight of 204.5-pounds at the start of the study for a "pretend" participant we can use as our baseline to do the math. You can double-check my assumptions with an online BMI calculator at the CDC website.

We do need to know something else though - what is the calorie intake at the start to maintain body weight of, let's just say, a completely sedentary person of this height and weight? For this number, we need a Basal Metabolism Calculator, which can be found online at Room 42's website. Here we find a "couch potato" needs 1,865-calories per day just to maintain her weight.

So, we have some good numbers to start with.

Now let's do the math. Let's assume she eats the higher calorie average - 1,500 per day. And, also let's assume she wound up in the group burning just 1,000 calories a week for her exercise. How much weight should she have lost if we apply the calorie theory?

Oh.....92.28-pounds in two years!

That's right - 92.28-pounds!

Remember, the calorie theory is all about "calories in, calorie out."

Calories in = average 1,500 per day...this represents a calorie deficit of 365-calories each day. But, let's call it 300-calories just in case she under-reported her food intake.

300-calories per day X 365-days = 109,500 calories x 2 years = 219,000 calories

219,000 calories divided by 3500-calories per pound = 62.57-pounds

Now we have to factor in the exercise calories burned each week.

1,000 calories per week x 52 weeks = 52,000 calories x 2 years = 104,000 calories

104,000 calories divided by 3,500-calories per pound = 29.71-pounds

Add them up...

62.57-pounds + 29.71-pounds = 92.28-pounds theoretically lost if the calorie theory holds true.

What happened? Where's the expected weight loss?

Yup - another hole shot right into the Calorie Theory - and no one is paying attention since the "stats" used look good enough.

Well, "good enough" here simply isn't good enough. When you see statistics thrown around like this, without real pounds and hard numbers assigned to fat pounds lost - do the math!

7 comments:

  1. Just quickly scanned your post, but are you taking into account the fall in resting metabolism and activity calorie burn as weight falls?

    ReplyDelete
  2. Her healthy weight (BMI 22) would be about 140, so at 140 the same exercise she did at 205 is going to only burn about 140/205 of the calories (not completely precise, since body composition would be different).

    Her resting metabolism at 140 would be more in the range of 1,500 calories, plus or minus (11 calories per pound, more or less).

    The weight loss would assymptotically approach horizontal as she got near 140 if everything were in balance.

    A weight loss of 65 pounds is not so far off from 92 pounds, and the 27 pound difference seems like it would be explained by the overall reduction in her metabolism to normal for a 140-pound woman as she approached her normal weight.

    ReplyDelete
  3. >>>Her resting metabolism at 140 would be more in the range of 1,500 calories, plus or minus (11 calories per pound, more or less).<<<

    To calculate her calorie requirements at her higher start weight, as a couch potato, I used her active metabolic rate, not her resting metabolic rate as the determinant of calorie deficit potential (theoretically since she is a made up participant).

    Because she increased exercise consistently, her active metabolic rate increased, even with the weight loss. That is the calorie requirement that counts in weight loss - the deficit created from all the calories you burn from basal requirements and your activity - your active metabolic rate.

    At a BMI of 32 to start, even with horrible body fat percentage, we're talking about probably a potential of 33% body fat - or at a start of 204 pounds, 67.3-pounds of fat weight.

    The maximum loss in the two years was just 7.2% of body fat - nowhere near 65 pounds of body weight, even if you calculated a high loss of lean body mass.

    The results here remain unimpressive - and disconnected from the calorie theory that holds the deficit should create a parallel loss in weight over time.

    ReplyDelete
  4. Are you just going from the newspaper account? In college I worked in the medical library and had the opportunity to read journal reports and newpaper accounts side-by-side. Long story short: I'd get a copy of the original study if I were you. I find that most researchers will gladly e-mail a PDF if you ask.

    Actually, why not call one of the researchers up? I've done that, and they are usually thrilled to get the attention.

    I'm not sure what you mean by "calorie theory," but it sounds a little ... paranoid/conspiracy theoryish. Are you saying that the second law of thermodynamics doesn't hold in the case of the human body? Or are you just an adherant of the "formerly obese metabolism slowdown" theory?

    ReplyDelete
  5. >>>Are you just going from the newspaper account? In college I worked in the medical library and had the opportunity to read journal reports and newpaper accounts side-by-side. Long story short: I'd get a copy of the original study if I were you. I find that most researchers will gladly e-mail a PDF if you ask.<<<

    You might want to read some more of my blog to understand how adament I am about going directly to the data and not relying on secondary sources for interpretation of the data.

    ReplyDelete
  6. >>>I'm not sure what you mean by "calorie theory," but it sounds a little ... paranoid/conspiracy theoryish.<<<

    A quick google search will provide you with enough definition that explains how deeply rooted the "Calorie Theory" (calories in - calories out) is within the medical, dietetic and scientific community - not at all conspiracy theory or paranoia - it is what it is.

    ReplyDelete
  7. You missed my point, I think. I know the calorie theory is deeply rooted, because it's true. :-)

    What is your alternative theory?

    If all you're saying is that the effect of exercise and food restriction seems to vary from time to time, all that means is that the body may be adjusting its efficiency. That's fine. But the "calorie theory" encompasses that.

    Give me some Google search terms to use to research the non-calorie theory.

    Also, you didn't specifically respond to my question about whether you used the original research report. You imply you did. Yes or no? You don't link to it. Generally such research is behind fee-walls and only abstracts can be read. (Annoying, since NIH and NSF money pays for much of it.) The fact that you link to the Fox News version of the article rather than the original WebMD version led me to believe you didn't put a lot of time into tracking down the original. By the way, Ms. Laino has footnotes on WebMD, and they only cite a press release, so even she doesn't seem to have seen the original research.

    A specific factual thing you seem to be assuming that is not in the WebMD story is that the exercise routine continued to burn 2,000 calories a day despite a changing metabolism. In other words, the researchers monitored the woman's metabolism and increased the exercise mandated as time went on. Is this more clearly stated in the original paper than in the newspaper article?

    ReplyDelete