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Are Grains Making Us Fat?

Megan McArdle

Are grains killing us--or at least, killing our New Years Resolution to lose some weight?  Karl Smith looks at this infographic and wonders:

As always, no one disputes that wedging will result in weight loss. That is driving calories-in and calories-out in opposite directions will lower the caloric content of the body. Excluding water there is a rough relationship between caloric content and mass. For most fat, which is our primary concern in obesity, the relation is about 3500 calories per pound.

The tendency of all animals is to try to get calories-in and calories-out to move in harmony. If you have to wedge then that means that this system has failed. At a minimum we would like to know why.

Historically people worked a lot more than they do now. They also ate a lot more than they do now. From the year 1400 to 1970 average calories expended fell dramatically but so did average caloric intake. Obesity was never a severe problem. The system did not fail.

Then from 1970 to 2010 average calories expended actually rose but calories consumed rose more and obesity exploded. The system failed.

If you go and look at the actual graph though, you can see Gary Taubes's thesis on display. This is natural since the dataset used to make the graph is one of Gary's favorites. First you see meat falling, then fat falling/stalling, then sugar falling as various healthy eating theories rose to prominence.

The only thing that rises consistently is grains. Gary insinuates and sometimes outright says that obesity was caused by the encouragement international health authorities for people to eat more grain. The naturally tendency is for people to eat more meat as calories become easier to obtain. He suggests that consciously overriding this mechanism led to an excess of insulin and possibly deficiency of peptide YY, which are key regulators of caloric balance.

I am skeptical of this theory, but it is one that at least recognizes the underlying theoretical problems.

I too am skeptical of this theory, and here's why.  It's totally true that if you look at the change in the American diet since the 1960s, grain consumption has gone up dramatically, growing right along with our waistlines.  The problem is that this is only true for the 1960s.  Check out my sadly less snazzy infographic showing the caloric contribution of various elements to the US food supply since 1910:

Food Supply.png

 As you can see, we have never gotten back up to the nearly 40% of calories from grains that we consumed in the early part of the 20th century.

Now, of course, food supply is not a perfect proxy for food consumption--but it's a pretty good proxy, especially in an era before massive farm subsidies.  Was it that all the grain consumed before 1950 was healthier whole grain? No.As flour became an industrial product in the late 19th century, mills began processing out the germ and other "whole wheat" elements because the fats in the germ caused the flour to go rancid.  By 1914, your great grandmothers were mostly baking with white flour.  Polished ("white") rice was similarly well established, and for some of the same reasons.  And of course corn, the other major American grain, does not have a healthier "whole" alternative.

To me, the Taubes theory only works if you start your dataset in the 1970s.  If you look earlier, you notice that our sturdy forebears were in fact giant balls of carbohydrates (the grain figure doesn't even include the two hundred pounds of potatoes Americans ate every year in the early 20th century.)  Yet they were not fat.

I hear a lot about Taubes' theory from people pushing the notion that "we're evolved to eat meat and fruit, not processed grains".  I mean, true as far as it goes--but it doesn't go very far.  A ribeye and an arugula salad with oilive oil and vinegar is almost as far from what our paleolithic ancestors ate as pasta primavera and an angel-food cake.  The meat our ancestors ate in the wild was not mostly fat-rich steak--game animals don't have that much body fat, and their muscles are a lot less tender.  We've selectively bred our domesticated animals for considerably more succulence than our ancestors enjoyed.  In the rich world, we've also stopped eating the "gamier", more vitamin-rich organs.  In fact, almost every fruit or vegetable you enjoy eating has been bread to be larger, higher-calorie, and full of less in the way of fibers and natural pesticides than what our pre-agricultural ancestors ate.

Yet it's only now that we're getting fat.  Which suggests to me that the cause is something other than the variation from our "natural", meat-rich diet.

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