If you burn 2,500 calories a day and consume 1,500, the IMPLIES that you WILL lose 2 pounds a week.
I see.
So that is 100 lbs a year. In a year and a half a 150 pound person will weigh approximately ZERO.
No, no they won't. And they won't starve to death either, because at 1,500 calories you can get all the nutrition you need. So the body will adjust in all kinds of ways to reduce expenditure. It does that as a survival mechanism. YOU WILL NOT STAY IN CALORIC DEFICIT.
There are quite clear studies that have documented this. The Minnesota Starvation Experiment.
Here is an excellent quote from "The Obesity Code" by Jason Fung. Basically he is saying that this simple model of Calories IN - Expenditure = Fat Formation is wrong.
"What determines the energy output of the system? Suppose we consume 2000 calories of chemical energy (food) in one day. what is the metabolic fate of those 2000 calories? Possibilities for their use include:
heat production
new protein production
new bone production
new muscle production
cognition(brain)
increased heart rate
increased stroke volume (heart)
exercise/ physical exertion
detoxification (liver)
detoxification (kidney)
digestion (pancreas, bowel)
breathing (lungs)
excretion(intestines and colon), and
fat production
...
There are an almost infinite number of ways that the body can dissipate excess energy instead of storing it as body fat.
With the model of the calorie-balancing scale, we assume that fat gain or loss essentially unregulated, and that weight gain and loss is under conscious control. But no system in the body is unregulated like that. Hormones tightly regulate every single system in the body. The thyroid, parathyroid, sympathetic, parasympathetic, respiratory, circulatory, hepatic, renal, gastrointestinal, and adrenal systems are all under hormonal control. So is body fat. The body actually has multiple systems to control body weight.
The problem of fat accumulation is really a problem of distribution of energy. Too much energy is diverted to fat production as opposed to, say, increasing body heat production. The vast majority of this energy expenditure is controlled automatically, with exercise being the only factor that is under our conscious control. For example, we cannot decide how much energy to expend on fat accumulation versus new bone formation. Since these metabolic processes are virtually impossible to measure, they are assumed to remain relatively stable. In particular, Calories Out is assumed to not change in response to Calories In. We presume the two are independent variables.
.....
Lets apply this reasoning to obesity. Reducing Calories in works only if Calories Out remains stable. What we find instead is that a sudden reduction in Calories In causes a similar reduction in Calories Out, and no weight is lost as the body balances its energy budget. Some historic experiments in calorie reduction have shown exactly this"
End of quote.
So as calories are reduced, the body has a problem. It has a set point for your weight. It also has a ton of other things it needs to expend energy on. But saving the body from starvation is pretty high up on the list! Tons of other systems can be reduced. And yes, if starvation is enforced severely and long enough, the fat will go. But the body has a grudge to grind. We do not live in a starvation society, there is no way in hell it is going to allow this state of affairs to continue. It will ensure that the systems are brought back to what it considers "safe'. Worse still, there is evidence that the body learns from the experience and, semi-permanently adjusts its fat goals higher to ensure that this never happens again.
In summary, the idea that fat level is the ONLY use of extra/less calories in is incorrect.
www.worldlifeexpectancy.com
