1 March 2014

Food for Thought

Fathoming the calorie. 
‘I have some trouble fathoming our constant questioning of the calorie: Is a calorie really a calorie? Do calories really count? After all, a calorie is a precise and specific unit of energy, or heat. Namely, it is the heat required to raise the temperature of 1 cubic centimeter of water at sea level 1 degree Celsius. The measure we more routinely apply to food, the kilocalorie, is exactly 1,000 times as much,’ writes Dr David Katz.

Dr David Katz
Dr David Katz

‘The quantity of calories we consume matters and it's the principal determinant of what we wind up weighing. The evidence that quantity matters is clear, consistent, and in my view, irrefutable. Fed an excess of calories, even if mostly from high-quality protein, people gain weight. Assigned to a calorie deficit, people lose weight—even if the calories are mostly from Twinkies. Calories count. But of course, quality matters too, and it matters on both sides of the energy-balance equation.

Calories go out in three ways: we burn them to survive (resting energy expenditure); we burn them to work (physical exertion); and we waste them (thermogenesis or heat loss). The quality of the fuel we consume can affect both resting energy expenditure, and thermogenesis. Is this surprising? Not at all. We can make fire with wood, or coal; coal burns hotter. Protein, fats, and low-glycemic foods seem to burn a bit "hotter" than simple and refined carbohydrates, a fact corroborated by a study in the Journal of the American Medical Association.

Quality matters considerably more, in my opinion, to the calories that come in. We all know the food industry's most famous threat: "betcha' can't eat just one!" Of course, it wasn't intended as a threat, but in an age of epidemic obesity, isn't it exactly that? Foods can, indeed, be processed into virtual irresistibility based on detailed studies of brain function, imaging of the human appetite center in the hypothalamus. And they can be processed into marvelously efficient calorie delivery systems: energy dense, nutrient dilute, low in volume.

Calorie rich, nutrient poor foods

Wholesome, nutritious foods have the opposite effect. Among their many virtues, they minimize the number of calories it takes to feel full, due to many attributes, among them: high volume, high fiber, low-glycemic index/load, nutrient density, energy dilution, flavor simplicity, etc. The following tips are as much about finding health as losing weight, so they are advisable whether or not you have weight to lose.
  • To control weight, you must control calories—quantity matters. Period! 
  • The best way to control quantity is by improving quality. One of the many virtues of wholesome foods is that they help us fill up on fewer calories. Eat lots of simple foods that are close to nature. 
  • More of the right kinds of fat can be helpful. Monounsaturated and polyunsaturated fats are generally good for health and may help with portion control in the right context. An example of that context is the Mediterranean diet. 
  • Protein is satiating. Up to a point, more high-quality protein can be helpful. Think lentils, beans, meats, fish, eggs. 
  • Lower glycemic load can be helpful. This does not require cutting carbs indiscriminately, but it does mean avoiding or limiting foods made with refined starches and added sugars. 
  • Foods can be high in calories, and still help control total calorie intake—if they are rich in nutrients, and help confer a lasting feeling of fullness. We have such evidence for walnuts and almonds. 
  • While the source of calories may influence how many are burned, this is a trivial effect compared to that of…exercise! If you really want to burn more calories, you will get far more out of changing what you do with your feet than by changing what's at the end of your fork.  
This edited extract is reproduced with Dr David Katz permission. It first appeared in Eat+Run In Dr Katz latest book (with Stacey Colino), DISEASE PROOF, he shares the very skill set on which he and his family rely to enjoy lifestyle as medicine.