When exercising how does the body distinguish which calorie to burn off?

A calorie is a calorie is a calorie to the human body. What food it came from doesn't matter.

Fragmoss wrote: »

If I use those 375 calories yet to eat in a way that's unhealthy. A food loaded with sugar or fat. How does the human body distinguish between already *good* calorie still in my body and then the add bonus *bad* calories I would now ingest into my body?

Calories are neither good nor bad...They just are.

If you have 375 calories to eat, and you eat 375 calories, then all is well on the calorie-counting front.

Now when you talk about the macro- and micro- nutrient breakdown of those calories, that is an entirely different conversation.

Most people suggest hitting recommended minimums for protein and dietary fat, and then filling out your diet with whatever macro combo works best for you. For micro- nutrients, I think most people find that as long as they eat a varied diet with an emphasis on whole foods, they tend to work themselves out without fretting too much.

Fragmoss wrote: »

How does the human body distinguish between already *good* calories still in my body and then the add bonus *bad* calories I would now ingest into my body?

It doesn't. You're seeing labels. Your body sees energy.

Biochemically and physiologically, fats are the best source of energy (ATP) in the body. But that's a detail, because the above posters are correct in that a calorie is a calorie. Exercise doesn't prefer one calorie that you ate over another.

Fragmoss wrote: »

How about if a person eats 1200 calories but all of the food is crap foods? Where are the nutrient's, minerals? So a person could be skinny are very unhealthy?

Even "crap foods" have some nutrients and minerals. But yes, being skinny doesn't mean that you are healthy. Skinny people can also get ill.

If I understand correctly, the body will use whatever calories are available from eaten foods first. When it runs out of those, it turns to fat stores. That's why you want to be at an overall deficit (which the 1200 calories plus 175 from exercise does for you).

As far as what kind of foods the calories came from, the body doesn't care, at least for energy purposes. Of course, you want to get a balance of macro nutrients and all the necessary micronutrients for overall good health. But as far as the body's energy use, it doesn't matter where the calories come from. (And even for overall health, a few treats are fine, too)

It's all chemicals to the body. There's sugar (glucose), but not good sugar and bad sugar.

Generally speaking, when called upon to release energy for exercise, the body uses the most efficient (in terms of speed and energy required to execute) processes first. Typically, glycogen stores go first. Carbs get broken into glucose. Metabolizing fat is a pretty efficient process (and is, after all, fat's purpose). Protein is broken into amino acids, and if the body doesn't need amino acids (or if the body runs out of other fuel), it would process those for energy. Each macronutrient has it's own pathways for generating energy.

Also generally speaking, the body will use first what it is least able to store. E.g. alcohol--that takes metabolic priority over everything else. If you've eaten lots of carbs and fat, the carbs will metabolize first. The whole "low fat" nonsense of the 60's and 70's was sort of predicated on the false notion that any dietary fat will be stored, but truthfully, how much fat get stored is completely dependent on the overall energy equation (CICO). I.e., if you eat tons of carbs, the body will store the little fat you do eat until carbs are processed, but if you eat few carbs and tons of fat, the body will metabolize fat because it is what it has.

Not sure if that addresses your Q.

TrailBlazzinMN wrote: »

stealthq wrote: »

TrailBlazzinMN wrote: »

I would love for someone to eat all of their fat from trans fat (the processed stuff) and let me know how they feel within a few days.

In a few days? Doubt they'd notice anything unless, in order to do that, they drastically changed everything they ate. But then it wouldn't be due to the trans-fats.

Trans-fats are a longer-term risk factor.

Doubt it hardly scientific. Eat 50g of trans fat in one day. Do it. I dare you.

And what else would have to go along with those 50g of trans-fats? What am I realistically going to eat to get 50g of trans-fats in a day?

DeguelloTex wrote: »

And what else would have to go along with those 50g of trans-fats? What am I realistically going to eat to get 50g of trans-fats in a day?

Doesn't matter. Supposedly a calorie is a calorie is a calorie to the human body. You can buy trans fat all by itself.

TheopolisAmbroiseIII wrote: »

To be more sciencey (but very general and not particularly precise), your muscles will burn the energy store within them (glycogen) first, then use blood sugar (glucose) when that is consumed, (blood sugar is harvested from or built out of the stuff you eat) and finally will go to your stored body fat when all the food energy is used up.

There's no preference given to 'good' or 'bad' foods by your body, because it's all just food.

You are absolutely correct in how the muscles use their sources of energy during exercise, but fat is more energetic than carbs or protein. (Also, skeletal muscle primarily uses fats at rest, not exercise.) Protein and carbohydrates both contain 4 calories/gram, and fat has 9 calories/gram. This is where the earlier poster made the error.

DeguelloTex wrote: »

TrailBlazzinMN wrote: »

Doesn't matter. Supposedly a calorie is a calorie is a calorie to the human body. You can buy trans fat all by itself.

For the purposes of energy, a calorie is a calorie. But I suspect you knew that. Plus, it has the benefit of being relevant to the OP's actual question.

The OP wants to know the difference between "good" calories and "bad" calories and people are saying "a calorie is a calorie is a calorie". This is simply not true. If it were true, our bodies would feel exactly the same whether we were eating 50g of fat from an avocado or 50g of trans fat. And we don't even need to do a test to prove that isn't true.

From a very simple energy standpoint, you are correct. However, that simplistic mindset does no one any good when it comes to the human body since it is an extremely complex organism.

TrailBlazzinMN wrote: »

I would love for someone to eat all of their fat from trans fat (the processed stuff) and let me know how they feel within a few days.

To be fair, OP asked about metabolic pathways for different nutrients. "How does the body distinguish..." She didn't ask about how different nutrients make you feel.

*shakes head*