Thursday, December 20, 2007

Montreal, Snow Storms and the role of carbs in weight loss

It's been a crazy week for me. I was in Montreal for the weekend, checking out the local cuisine. I had some very tasty duck, and some amazing raw fish at Buona Notte (I highly recommend this restaurant!) Unfortunately, on Sunday I was caught in that huge snow storm that pummeled southern Ontario. Needless to say, what should have been a 6 hour drive home ended up taking almost 11 hours!

By the time I finally got home I was so behind on work that I had to spend the last couple days trying to get caught up on emails. One of the emails I received had a really great question asking whether it's carbs or calories that causes weight gain. I've copied the question and my answer below...

Hi Brad,

I've read your book Eat Stop Eat and I'm wondering whether you would have written it differently now that you've read "Good Calories, Bad Calories" by Gary Taubes. I mean, in your book you still write as if the amount of calories matter and as if you shouldn't differentiate between them. What Taubes has found is that the only thing you really can say is that too many Carbs are unhealthy.


And here is my answer:

Hi George,

Thanks for the email and for the excellent question.

I have read "Good Calories, Bad Calories" and was very impressed with its content. I believe that Taubes has accurately pointed out the health issues surrounding a high sugar intake. However, I do not believe that he accurately analyzed the data regarding the correlation between total calories and obesity.

Taubes examined studies containing diet record data and concluded from this research that the obese do not eat any more calories than non-obese people. Unfortunately, we have learned from the work of Brian Wansink that obese people tend to under report their caloric intake by as much as 30% when using diet records. This phenomena has been noticed by other researchers, and has been written up as an extremely important confounder in weight loss research. (For a great write up on this point you can see a Trial by Steven W. Lightman et al. published in the New England Journal of Medicine, volume 327 (37), 1992.)

For this reason I would not have changed any of my recommendations in Eat Stop Eat if I had read "Good Calories, Bad Calories" before I began writing.

I think that the points that Taubes makes about sugar are accurate, and I do believe that one or two 24 hour periods of complety no sugar (like during the Eat Stop Eat method of fasting) is beneficial to human health, yet I also believe that the only way to reduce body weight is through a negative caloric balance, and the best way to ensure that the majority of that weight loss is fat is by using the combination of caloric restriction and resistance exercise (the two keys to Eat Stop Eat's success).

I hope this answer helps,


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David Brown said...

Hi Brad,

I am a nutrition science analyst. I've spent thirty years exploring both popular nutrition literature and the scientific journals, trying to make sense of paradox and controversy.

Surprisingly few scientists and weight control experts pay attention to where ALL the calories go. This, I think, is why I often see statements such as these: "... the only way to reduce body weight is through a negative caloric balance, and the best way to ensure that the majority of that weight loss is fat is by using the combination of caloric restriction and resistance exercise." Your first statement about negative caloric balance, while technically true, is an oversimplification. Allow me to explain why.

Several hundred years ago Benjamin Franklin said, "You are what you eat." Several decades ago biochemist Ross Hume Hall, PhD in his book "Food for Nought" observed, "You can't be more than what you eat." A few months ago Michael Pollan commented, "You are what you eat eats." And more recently in the Journal "Lipids" Jeff S. Volek pointed out, "You are what your body does with what you eat."

So, what all does the body do with food calories? Obviously, many of them are used to fuel the body's chemical reactions. But some of them are also used to fuel the chemical reactions of those trillions of tiny guests in the digestive tract which, in turn, generate heat. Bacterial heat, in conjunction with the heat released by other chemical reactions such as those taking place in muscles and brown fat tissue, helps keep the body warm.

If a person increases his caloric intake, there can theoretically be a corresponding increase in bacterial activity in the digestive tract without any significant increase in caloric absorption. Moreover, if one increases fiber intake, there is a corresponding decrease in absorption efficiency.

My son-in-law is a body builder. He consumes many thousands of calories each day to maintain his weight where he wants to keep it. He also generates enormous amounts of heat and wears light clothing even in cool weather.

My own experience eating a high fat diet is that my weight stays level no matter how few or many calories I consume. If I eat more calories I have more bowel movements and vice versa.

So it's not exactly as you imagine, Brad. The body compensates both hormonally and physiologically to changes in caloric intake. With caloric restriction the metabolism slows, brown fat tissue shrinks, the stomach enlarges, and the small intestine develops more surface area. There's also less rebuilding of muscle tissue, less production of hormones, slower transit time for material passing through the digestive tract, and even loss of organ and bone tissue.

There's very little well designed experimental research demonstrating weight loss in conjunction with increased fat calorie intake. The one good study I know about can be accessed by Googling "Penelope J. Greene Harvard".

David Brown
Nutrition Education Project

Brad Pilon said...

Hi David,

Thanks for the comment. I think you raise some interesting points regarding the role of the micro flora of the gut in human health. However, I still believe that the primary regulatory of the weight of a human (or any animal) is total calorie balance.

I think as nutrition researchers we can both agree that reducing caloric intake in any species will reduce body weight, and that this response is dose dependent and if left for chronic periods can result in enough weight loss to result in mortality.

This response is, as you rightfully stated, regulated by a very complex reaction between hormonal, bacterial, and psychological adaptations. However this regulation can only happen within tightly defined parameters. As we know, the absolute removal of calories chronically from the diet will ultimately lead to death, so caloric intake will always factor into this equation.

My only concern with your comment are the following statements:

" brown fat tissue shrinks, the stomach enlarges, and the small intestine develops more surface area. There's also less rebuilding of muscle tissue, less production of hormones..."

To the best of my knowledge the human species does not have any discernable brown fat by adulthood. Also, during caloric restriction there is actually an increase in both proteolysis and non oxidative leucine disposal, leading to the suggestion that there is actually increased protein cycling and remodelling during caloric restriction, and there is definitely some hormones that see a decreased production (insulin) but others that are increased several fold (growth hormone)

I think a lot of the confusion around dieting and nutrition comes from the interpretation of scientific studies, the applicability of their data to larger populations and our inability to tease out many of the pychological confounders that are hidden within weight loss research.

You raise some very good points regarding the regulation of the “calories in” side of the equation, but it is still ultimately controlled by the availability of calories to the body.and as you point out, any microorganisms it may be hosting.


David Brown said...

Brad, Have you read "Biochemical Individuality" by Roger J. Williams, PhD? I see a lot of debate regarding what constitutes a "proper" diet or the "best" diet or the "most effective way" to lose weight. Much of it likely stems from our very human tendency to view the world from a limited educational perspective and generalize from personal experience.

Regarding brown fat tissue, I suggest you read Chapter 12 of "The Life Extension Weight Loss Program" by Dirk Pearson and Sandy Shaw. There's also some discussion on page 89 of "How to Lower Your Fat Thermostat" by Dennis W. Remington, MD, A. Garth Fisher, PhD, and Edward A. Parent, PhD.

From Wickipedia:

"When growing up, most of the mitochondria (which are responsible for the brown color) in brown adipose tissue disappear, and the tissue becomes similar in function and appearance to white fat - as a mere fat deposit. However, recent studies using PET scanning of adult humans have shown that it is still present in many adults in the upper chest and neck. The remaining deposits become more visible (increasing tracer uptake) with cold exposure, and less visbile if an adrenergic beta blocker is given before the scan."