“When Atwater burned foods in a bomb calorimeter… he assumed that humans could use all the energy present in a food and digested in the body. If foods burns in the bomb calorimeter, Atwater seemed to conclude, it produces the same amount of energy value in our bodies. But the human body is not a bomb calorimeter. We do not ignite food inside our bodies. We digest it, and we use calories to pay for this complex series of operations. The cost varies…”
~Richard Wrangham; Catching Fire
Tis the season for people to start making New Year’s Resolutions to lose weight. Oh what fun! And so, I figured what better time to do a multi-part series on the huge scientific fallacy and oversimplification that is, for lack of a better phrase to describe it, The Calorie Theory.
For a half decade I have been tediously challenging the idea that cutting calories can lead to sustainable weight loss. If the medical literature is any indication, it is not. Sure, there are success stories, and there are methods that involve being at least somewhat calorie conscious that may indeed work – due to the combination of factors involved in the system as a whole. But overall, from a statistical point of view, cutting calories in an act of “intentional weight loss” is a useless, short-term fix at best. And, “the single greatest predictor of future weight gain” according to Paul Campos at worst.
And in the process of trying to illuminate this fallacy, I really strove to find a way to eat a lot of calories and either stay lean or actually lose body fat. Instances where I, for example, ate 4,000 calories of raw fruits and vegetables and still lost body fat was something that I looked at as being evidence that calories are definitely NOT the only factor involved with weight loss. Or how about the example of the gorillas in captivity that DOUBLED their calorie intake and still lost a considerable amount of weight? And of course everyone wonders how the raw vegans like Freelea and Durianrider manage to eat more calories than is normal for males and females of their age, height, weight, and activity levels and still look like emaciated prepubescents. Or hey! What about that Jon Gabriel guy who eats “whatever he wants,” but always adds lots of live foods and whey protein and has lost 200 pounds? These all seem like very interesting contradictions to the calorie theory. Do they disprove it in any way? No. Because these phenomena are all very easily explained.
It appears that I, as I so often do, have overlooked some important variables that aren’t normally accounted for in The Calorie Theory. While I (and Stephen Guyenet) have talked at great length about palatability, and how factors in palatability such as water content, fiber content, calorie-density, sweetness, chewing time, and particle size affect the number of calories we have an appetite for automatically – it seems there is something else about these foods of great importance that make them very different from other types of food…
We absorb fewer calories from such foods. And the difference is not small. It’s huge. The biggest differentiating factor probably being whether a food is raw or cooked.
This may not seem like a major thing, but in a world where the calories in a doughnut and the calories in raw apples are on an equal playing field, this turns the entire world of calorie counts and food labels completely on its head – because you absorb a lot more of the energy in 500 calories of doughnuts than you do 500 calories of apples. And, thrown in there with that, is the huge variability in the digestive capability of one person compared to another. One person might absorb 400 of the 500 calories in a bag of raw apples while another can only absorb 250.
This is even more important as it pertains to humans, as humans have the weakest digestive tracts of any creature. Our digestive tracts have changed over the millenia to be small and weak for the same reason our muscles have (compared to other primates especially)… because we don’t need them. Why divert energy to stellar digestion (diverting energy from brain development as some researchers such as Leslie Aiello and Peter Wheeler have proposed) when we can chop and cook and blend and crush the heck out of our food to make it maximally digestible? For the same reason, humans have really small mouths per pound of body mass compared to all other primates – most of which spend 5-8 hours per day chewing.
So what about the gorillas that doubled their calorie intake and lost tons of weight? It turns out gorillas only absorb about 50% of the calories they ingest from “browse” or leafy matter – the natural diet of a gorilla (and keep in mind their digestion of plant matter is vastly superior to our own).
What about Jon Gabriel who eats lots of raw nuts and seeds, sprouts, and eats everything in a big, giant salad? With lots of protein? We absorb fewer calories from protein due to the increased cost of digestion, and fewer still from raw foods – to the point that the Giessen raw foods study done on raw foodists showed a horrifying frequency of underweight and amennorhea directly proportional to the degree in which the percentage of the food eaten was uncooked. This obviously explains away the raw vegan waifs as well, along with the known hypermetabolic effect of protein restriction and calorie-wasting effect of fat restriction. Big parts of the 80-10-10 Low-fat raw vegan diet. Oh the irony of calorie restriction bashing while inadvertantly restricting calories!
There is much more to the story here than meets the eye, and it all makes for very interesting thought for food. Thanks to highly intelligent author Richard Wrangham and the fair maiden that gifted his book to me on my 20,000 mile pee parade this summer. Enjoy this passage from Catching Fire: How Cooking Made Us Human pertaining to the human inability to absorb sufficient energy from raw foods, with a subtle condescension that is beyond priceless…
“To judge whether the energy shortage experienced by raw-foodists is biologically significant, we need to know whether raw-induced weight loss interferes with critical functions- ideally, for a population living under conditions similar to those in our evolutionary past. In the Giessen study, the more raw food that women ate, the lower their BMI and the more likely they were to have partial or total amenorrhea. Among women eating totally raw diets, about 50 percent entirely ceased to menstruate. A further proportion, about 10 percent, suffered irregular menstrual cycles that left them unlikely to conceive. These figures are far higher than for women eating cooked food. Healthy women on cooked diets rarely fail to menstruate, whether or not they are vegetarian. But ovarian function predictably declines in women suffering from extreme energy depletion, such as marathoners and anorexics.
Raw-foodist men sometimes also report an impact on their sexual functions. In How to Do the Raw Food Diet with Joy for Awesome Health and Success, the author, Christopher Westra, wrote: ‘In my own experience, starting on living foods brought about a change in sexuality that was dramatic and completely unexpected. In just a few weeks, the number of times per day I thought about sex decreased tremendously.’ Westra believed that seminal emissions are designed to remove toxins from the body. After a few weeks of a raw diet, he said, the intake of toxins had fallen to the point where ejaculation was no longer necessary. In a similar way some raw-foodists regard menstruation as a mechanism for removing toxins and therefore regard its cessation as a sign of the health of their diets. Perhaps it is unnecessary to note that medical science finds no support for the idea that toxins are removed by seminal emissions or menstruation.
Reduced reproductive function means that in our evolutionary past, raw-foodism would have been much less successful than the habit of eating cooked food. A rate of infertility greater than 50 percent, such as was found in the Giessen Raw Food study, would be devastating in a natural population of foragers. And since the Giessen study was of urban people enjoying a life of middle-class ease, such dramatic effects on reproduction are mild compared to what would have happened if these German raw-foodists had been searching for food in the wild.
Most raw-foodists prepare their food elaborately in ways that increase their energy value. Techniques include mild heating, blending, grinding and sprouting. Any system of reducing the size of food particles, such as grinding and crushing, leads to predictable increases in energy gain. The German raw-foodists also had the advantage of eating oils produced commercially by industrial processing. Koebnick’s team found that about 30 percent of the subjects’ calories came from these lipids, a valuable energy source that would not have been available to hunger-gatherers. Yet even with all these helpful conditions, at least half of the German women eating raw foods obtained so little energy from their diet, they were physiologically unable to have babies.”