In the September 2013 issue of Scientific American, the topic is nutrition. One of my heroes in the nutrition science wars is Gary Taubes, and he authored an article in this magazine.
Taubes frames up the critical debate about how to be healthy and lean between two camps -
1. Calories in, calories out, or "a calorie is a calorie", or "just eat less and move more", which is essentially a moral story - "people get fat because they are gluttonous and lazy."
2. The carbohydrate or alternative hypothesis, or the "hormone hypothesis of obesity" - consumption of excess carbohydrate leads to a cycle of high blood sugar leading to high insulin levels which biases the body towards storage of ingested carbs as fat, but also makes us hungry and makes us feel lethargic. In other words, "People feel lethargic, and accumulate body fat, because they induce hormone dis-equilibrium through excess carbohydrate consumption."
There are folks in both camps who are quite persuasive, but of course, that's the rub - if the science on the matter was conclusive, there would be no need to persuasiveness! Let me provide what I see as the main lines of argument from the two camps:
The laws of thermodynamics are clear - for a body to gain or lose energy (aka fat which is stored energy), the body must ingest more energy than is expended, or ingest more energy than is expended. In other words, it is a simple matter of mathematics - reduce caloric intake and increase caloric expenditure to induce an energy imbalance. Anyone who is gaining weight, or cannot lose unwanted weight, is simply too lazy or too gluttonous.
And, we get sick because being fat makes us sick, so diseases such as insulin resistance, metabolic syndrome, and ultimately type II diabetes result from the obesity created by an energy imbalance that lazy, gluttonous populations routinely create for themselves.
Some things that might be worth considering to fully consider this perspective:
-Just because a gram of fat creates 9kcal of energy when combusted in a bomb calorimeter, does that mean it always adds 9 kcal of energy to our bodies every time we eat a gram of fat? Ditto for carbs and protein - do we really know how many of the potential units of energy we receive from each gram of the various macronutrients we ingest? Interestingly, there's an article in the same Scientific American which seems to indicate the answer is "no". In other words, a potential calorie in food is not always a calorie of energy in the body.
-If a "calorie is a calorie" is such a simple matter of mathematics, why in all of the studies done on such matters has no one every lost the forecast amount?
-If a "calorie is a calorie" is in fact the guiding principle of fat loss, we are all screwed; if we miss our calorie calculation each day by 20 kcal, which for me would be an error of less than 1%, we will gain a pound of fat per year. Considered from this perspective, as Taubes has pointed out, it's a miracle we are not all carrying the spare tire.
-All fat people are not sick; why? Some people who are relatively skinny are sick in the same way as sick fat people (loss of glycemic control); why?
-In many intervention studies which test low carb v. high carb diets, folks on a carb restricted diet spontaneously reduce caloric intake. In correlation with carbohydrate restriction, many sick people begin to get well before they get lean; gout, hypertension, and non-alcoholic fatty liver disorder, for example, can be reduced in as few as 3 days of carb restriction.
-We can observe that folks accumulate excess fat differently. For example, endomorphs always have more sub-cutaneous fat than ectomorphs - if fat accumulation is just a matter of calories in, calories out, why do bodies allocate fat differently based on phenotypes?
-Why do pregnant ladies and people in puberty eat more? Certainly no one would suggest their appetites changed because they became lazy and gluttonous.
-How is it that we could have such excess "energy" stored as fat, but still feel hunger?
-How could we interpret the well known phenomenon of caloric restriction over time leading to the "starvation effect", in which the metabolism slows, and fat re-accumulation is nearly inevitable?
Here are some answers which may be tested via Taubes' NuSI - the Nutrition Science Initiative, which was founded to test these two hypotheses - to see if science, despite the incredible challenges of doing it well on the human animal, can point to one or the other as more correct for more people.
-Sick fat people are those who have glycemic dis-regulation, healthy fat people have not lost glycemic regulation, because they are not insulin resistant. Why these people are fat isn't clear, it could be they ate too many carbs for a time and now are at a "maintenance intake" of carbs but not a fat loss intake. However, it is possible to discern a healthy fat person from a sick fat person just by looking (at least in some cases) at their faces. You can see this in the "Biggest Loser", as the contestants all arrive with their fat, sick faces but soon their faces shift to the "healthy but fat" face. If you've seen that show, you know what I mean.
-How come I could eat anything I wanted when young but now I can't?
I think this question may be where fructose comes into play. There's some evidence that fructose pushes us over the edge into insulin resistance, by essentially forcing the liver to work too hard processing fructose, so that it cannot do what insulin commands it to do. As the body secretes more insulin to get the liver into gear, other cells in the body risk damage due their responsiveness to insulin. They seem to protect themselves through insulin resistance. That creates a re-inforcing loop for insulin and blood sugar levels that seems to drive us towards metabolic syndrome. Metabolic syndrome leads to everything bad - diabetes which then is a predictor for gout, hypertension, stroke, alzheimer's, heart attack, etc.
One way or the other, due to Taubes' passion and his unrelenting focus on how much the existing science does not answer, but could, I think Gary will end up fundamentally changing how science and nutrition are pursued in our lifetimes. We may be only a year or two away from preliminary results from NuSI's first experiments. That's amazing!
The stakes are enormous. Between the insanity in the way our government tries to provide and regulate health care, and the remarkable and accelerated pace that our population is getting sick, and the vast array of medications that our health care system will provide to people to keep them alive while sick; our health care system is wrecking the fiscal health of our federal government.
Every day, I see and confront an amazing amount of mis-information about what a "healthy" diet is or is not. If the science could get us to the point of all knowing what makes us sick, it would be an incredible step forward. Go Gary go!