We Get Fat Because We Eat Too Much, or Vice-Versa

This past weekend my wife and I traveled up to Vermont with friends for some skiing, snowshoeing, and lots of good food.  I’ll be writing about the trip soon, but the focus of this post is about a book that I was able to read while I was there.  This book, titled “Why We Get Fat“, focuses on the role of carbohydrates in obesity.  Its author, Gary Taubes, is a science writer who does two things very well in this work.  He makes somewhat complicated subject matter very accessible to his readers, and his conclusions do not stray far from where the data leads.  An unusual combination indeed.

The premise of the book is simply that we have cause and effect backward when it comes to thinking about fat.  Our (very recent) conventional thinking, which by the way is almost wholly unsupported by data, is that you get fat because you take more calories in than you burn off.  It could be stated like this:

We get fat because we eat too much and we are lethargic

Taubes very ably turns that statement on its head:

We eat too much and we are lethargic because we get fat

At first glance this seems counter-intuitive, and even contrary to basic medical facts.  Everyone knows that you will put on weight if you take in more calories than you burn off, right?  This has been the consensus of the health authorities for at least a generation or two – that many people simply couldn’t have gotten it wrong.  Not this badly.  In the coming days and weeks I’m going to explore many of the ideas presented in the book in detail (I hope you come along for the ride).  In the meantime I’ll leave you with a few points to ponder, some from Taubes’ book and some from elsewhere:

Conventional Wisdom

First, the idea that the conventional wisdom parroted by health authorities may not be supported by actual data is not new.  I’ve occasionally highlighted examples on this blog – remember when salt was considered a health risk?  Oh yeah, it still is, but not because there is much data to support it.

A Slice of Bread

Now, let’s try a little thought experiment (similar to one presented in Taubes’ book).  Let’s follow two imaginary people from ages 20 to 60.  They are both men, and at age 20 they both weigh 150 pounds.  At age 60, one has put on a little weight, and is now 160 pounds.  The other is 450 pounds.  He’s gained 300 pounds in the same period of time.  Mr. Heavyset surely ate a lot more and probably exercised considerably less than Mr. Slim during the 40 years.  Calories in must have been way more than calories out, no?  Assuming 3500 calories per pound (an estimate to be sure, but reasonable), Mr. Slim has consumed 35000 calories excess calories over 40 years, and Mr. Heavyset has consumed an additional 1,050,000 calories. Now, let’s divide this by 40 years, and 365 days per year.  According to my rough calculations, Mr. Slim took in ~2.4 calories per day more than he burned off, while Mr. Heavyset took in an additional 72 calories per day.  The difference is ~70 calories per day, which is approximately a slice of bread.  That’s the difference between modest weight gain and tripling body weight?  Now let’s further assume that 2000 calories is an appropriate daily intake for both Mr. Slim and Mr. Heavyset, allowing them to maintain their 150 pound bodies by eating healthy meals such as the one shown  below (courtesy of Can You Stay For Dinner):

• Breakfast:  1/2 cup dry old fashioned rolled oats + 1 banana- both cooked in 1 cup lowfat milk +1/2 cup water, and 1 tablespoon peanut butter
• Lunch:  a salad consisting of 3/4 cup plain lowfat yogurt, 1 cup fresh fruit, 1/4 cup granola, and 2 teaspoons jam or honey
• Dinner:  pulled pork on a whole grain bun, 2-3 cups of vegetables
• Dessert:  2 chocolate chip cookies and a cup of lowfat milk

If we accept the calories-in/calories-out hypothesis, then what we are saying is that Mr Heavyset tripled his weight by eating, on average, an extra slice of bread per day.  Doesn’t this seem too simple?  Doesn’t there have to be more to the story than this?  If an extra slice of bread per day is truly all that it takes, why isn’t everyone morbidly obese?

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