Looking over the coming AAAS* meeting, this session drew my eye: Why a Calorie Is Not a Calorie and Why It Matters for Human Diets. In particular, I was drawn to the upcoming presentation by Harvard’s Rachel Carmody, who will be presenting “Contributions of Food Processing to Dietary Energy Harvest.” It seems that the work is in an early stage (processing in this case means, well, you can see for yourself):
The caloric consequences of a highly processed diet have remained unclear, in part because few studies have evaluated energy gains associated with a processed diet independently of other lifestyle factors, and in part because the metabolizable energy values reported widely in the scientific literature and on nutrition labels suggest that food processing has little caloric effect. However recent controlled experiments in our lab employing animal models show that processing by thermal and/or non-thermal means contributes importantly to energy harvest from plant and animal foods. For instance, controlling for food intake and activity, omnivorous adult mice exhibited increased body mass outcomes when eating cooked and/or pounded sweet potatoes or cooked beef versus when eating these foods in unprocessed form. Related experiments revealed these incremental net energy gains to be attributable to higher rates of nutrient assimilation in the small intestine as well as reduced diet-induced thermogenesis, the metabolic cost of digestion. These aspects of digestion are not represented in the Atwater factors typically used in the determination of metabolizable energy value. Thus researchers who report Atwater-based energy values as well as consumers who utilize nutrition labels to manage their caloric intake will necessarily underestimate the energetic gains associated with a processed diet. Given the long human history of food processing and its universal practice among modern populations, future work to improve our understanding of the energetic consequences of a processed diet promises fundamental insights into human biology, the energetic gains that fueled our evolution and the resulting commitments to an energy-rich diet that now sometimes threaten us.
What does this mean (for my purposes here)? One, as I said, this seems to be an early stage–cooking or pounding, while quite certainly processing (and showing the pedigree of food processing to be quite, quite older than the modern era) are arguably much different from industrial processing (with various stages of refinement, separation, adulterants and additives, altered “flavor packs” in “pure” products, low-fat, omega-3-added, etc. etc.). It is of course, without further information, a somewhat open question as to whether these additional, evolutionarily novel processing methods amplify or decrease the kinds of differences Carmody found. But I have for a while been wanting to write a little on how processed food may represent one way food industry is getting around what Michael Pollan has called “The Problem of the Limited Stomach.”
That is, unlike many other consumer products, food demand has a physical upper limit in terms of how much consumers can, you know, consume, even if they wanted to. There’s only so much space in the body (even if many of our bodies are becoming more, let’s say, more spatially accommodating). However, if a “calorie isn’t just a calorie”, that is, if some food is processed by the body differently, then some of this problem is worked around. I have a suspicion that the easy availability of cheap, simple carbohydrates (sugar) is not simply a result of subsidies or ease and availability of raw materials. While it may be only a “happy coincidence” for industry that sugars are available cheaply in many (most?) modern food systems, it also seems to be the case that simple sugars don’t provide us why as much of a sense of “fullness”, and so we’re able to eat more and more beyond what our body needs without the same kind of feedback that our body don’t need no more. In other words, you can’t make our stomachs bigger, but if you can get us to pump more stuff through it at higher and higher rates, and sugar is an efficient way to get more and more dollars/calorie through our bodies, well, like I said, at best it’s a happy coincidence for industry.
This is one of the challenges of many of our contemporary problems. While there are many compelling reasons to view alliances with commercial entities as important–possibly vital–to changing our food systems (among other systems), an important question has not been resolved to my mind, and is all too often avoided: what do we do in cases where the interests of the public are directly inimical to the (currently expressed) interests of most commercial systems? That is, many of us obviously need to be eating (and WASTING) much, much, MUCH less food. This would seem to require one or more of the following things:
- Charging more per calorie (i.e., decreasing the affordability and therefore effective demand for food); unfortunately, this poses difficulties for the significant portion of people, even in the Minority World (richer countries), that can’t currently reliably buy enough to eat–I’m looking at you, my foodie resident state!;
- Decreasing, through other means (including community organizing, community coalitions and education, and regulatory levers) the amount of calories people buy–which would seem like to directly decrease profits in the food system;
- Increasing the prices of unhealthy and/or heavily processed raw materials (which would likely both decrease food system profits and increase consumer prices in the absence of some fancy reorganization or new regulations).
1, 2, and 3 are not at all mutually exclusive (obviously, especially as #3 would likely cause 1 and 2). And they’re not enough–decreasing calories <> (is not equal to) better health. Eating the right foods and promoting a more active society are vital elements that will need to be addressed with the complex social determinants of health and relevant issues of inequality in mind. BUT, if processing itself may mean that we get more calories from the (nominally) same food product, then the implications would seem to be clear: we’d be better off eating less processed food. How we can work within the current system when that means paying more, buying less, and reaping lower profits is, let us say, quite a conundrum. (One I don’t find insoluble–I think system change is possible, and indeed, inevitable–what is not inevitable is positive changes to the food system, but I think it is certainly possible. We can do it! Nevertheless, a topic for another time…)
*The American Association for the Advancement of Science, publisher of the preeminent journal Science and reportedly the world’s largest scientific society…