How does metabolism work?

adelestarkhdp

I have this question that is in my mind for a while. If there is a person that want to lose weight and his basal metabolism is of 1500 calories. If he want to lose weight he has to eat 1200 calories. But if he also work out every day and with his cardio session he burn 500 calories, does he has to eat 1700 calories? Because I read that if you want to lose weight and you eat 1200 calories but you burn 600 calories, you introduce into your body just 600 calories, and you do lose weight but also ruin your metabolism. Is it true? If I have to maintain my weight, and I ate just 1200 calories, but burn 700 and I don't reintroduce those, what is going to happen to me and my metabolism? Thanks a lot for the answers, and I hope I explained well the question

Pearsquared

To start off, one should not eat below their basal metabolism. They should eat between their basal metabolism and their TDEE, which is the amount of calories they actually burn on a daily basis, which includes exercise. You can calculate that here: http://iifym.com/tdee-calculator/

Myfitnesspal, by default, uses the NEAT method, which has you set an basic activity level that does not include traditional workouts, which you add in yourself, but essentially, it works the same as TDEE in that you eat your exercise calories.

To answer your question, however, your metabolism can handle quite a lot before it shuts down. It takes a habit of extremely low calories to mess with it to the point where you cannot return it to it's original point or close to that through reintroduction of a normal diet.

However, there are other symptoms. Fatigue is by far the most common. You're basically not feeding your body the calories it needs because you're burning those calories off in exercise. Because of this, your body shifts from keeping itself comfortable to keeping itself alive. It will shift all of the few calories you give it to things like organ function, especially your heart and lungs. It takes a lot of calories to keep you warm and alert, so you'll start to feel cold all of the time and will have trouble thinking quickly, focusing, and remembering things. Next, your skin and hair may start to feel dry and brittle because these are non-essential functions. Basically, you'll be making yourself miserable for no good reason.

Mr_Knight

To start off, one should not eat below their basal metabolism.

There's no actual support for that claim.

The bottom line is that the less a dieter eats, the more attention they need to pay to their macros and nutrient levels, as the margin for error gets ever smaller. Somewhere down around 900 calories for a 150 lb person or 1200 calories for a 200 lb person (exact number varies depending on body fat percentage) it starts becoming more or less impossible to meet the body's macro/micro requirements. Those numbers are both well below BMR for that body size.

To answer the metabolism question - it is quite difficult to "wreck" your body's metabolism. Even if you ate at a huge caloric deficit (eg 1000 calorie deficit per day through diet alone) and lead a sedentary life, at the end of it, your base metabolism would have slowed down by perhaps 200 calories/day. To undo that will take 6-8 weeks of concerted effort, involving eating more and exercising more.

In terms of eating back exercise calories, a great many dieters get in trouble because it is even easier to over-estimate calorie burn than it is to under-estimate calorie intake. IMO, for most people, the path to success is paved by starting out NOT eating exercise calories, and then IF the body is struggling to exercise or weight loss is too fast, add back exercise calories in 100 calorie/day increments until that rectifies itself.

Pearsquared

Wrong post!