Luxus.. say what?
Before the turn of the century, German investigators did careful measurements on themselves and dogs. They noted that when they ate more than usual, the increased Calories could not be accounted for in the weight they gained except for the first few pounds. Then their weight stabilized even though they kept eating more. They couldn't find where the extra Calories were going. They weren't in the stools, they weren't in the urine, and they stopped gaining weight. They figured that the body must turn on a metabolism that ran only when it got fed too much. They called this metabolism Luxuskonsumption.
Luxuskonsumption gives it a German name but doesn't explain anything. Scientists divide energy expenditure in the body into several compartments. First is the cost of eating itself, called diet induced thermogenesis (DIT) or specific dynamic action (SDA) or the thermic effect of feeding. This depends on how much you eat and exactly what you eat. It is the cost of absorbing and handling the food. It usually represents about 10% of the Calories you ingest. Next there's basal metabolism. Basal metabolism is the energy requirement of doing nothing. It is the metabolism that must be maintained at all times to stay alive. It is the rate at which Calories are burned when you are at complete rest in a comfortable environment several hours after any food intake; something like what you're usually doing at 3 a.m. in the morning if you are not having a nightmare about how fat you are. Basal metabolism is necessary to maintain the integrity and readiness of all your body processes and to keep your brain doing whatever it does. For most people who don't run marathons or race in the Tour de France, this is where most of your food goes.
Basal metabolism is increased by wounds, burns, surgery, pregnancy, fever and other stress. It is decreased by dieting, starvation, malnutrition, and increased age.
Basal metabolism correlates with your size, or more exactly, with the size of your lean body mass. Lean body mass is the fat free part. Age and sex and surface area also factor into determining your basal metabolism. There is also some familial tendency. Your basal metabolism is like your parents' or brother's. After all these things and others are considered there is still some individual variation.
Obese people as a group have the same average basal metabolism as thin people. Actually obese people have an increased basal metabolism because they have more lean body mass together with the extra fat and they have more surface area. When we correct for the extra lean body mass and surface area, then obese people fall back into the middle of the bell shaped curve of basal metabolism, at least as near as the most sensitive instruments can detect. The final two places that the energy you eat can go are exercise or "non-resting energy expenditure" and stored fat. We'll talk about exercise and fat later.
So back to the Germans and their dogs. In which of these energy compartments can we put this Luxuscontraption? A further question that comes to mind is - Do we waste Calories and conserve Calories with the same metabolic machinery?
The answer is, "yes." All the compartments - thermic effects of eating, basal metabolism, and non-resting energy expenditure, contribute and they all work together in each direction. All of these conspire against us when we presume to change God's will.