The body's energy usage

Andaw

I would like to get a bit more of an understanding as to how the body works when exercising. My understanding is that the body uses the calories we eat as energy to carry out all functions, not just when we're exercising, including breathing, keeping the heart beating, etc, so we are constantly burning calories, even during sleep. Therefore consuming less calories than we burn will result in weight loss - I get that, it's simple maths!!

However, when it comes to exercising, I think the body converts certain types of calories in different ways. For example carbs are the easiest form of calories for the body to convert to energy, therefore it burns those off first, so by restricting carbs, it forces the body to use other forms of enegy, such as stored fat. However, I'm reading on MFP that if you're not careful, and you do too much cardio you could be burning muscle, which is not so good. I just don't really get how the body works.

I really am confused, anyone out there who has a good understanding of how the body uses energy? I go to they gym and do resistance as well as cardio, also fitness classes such as circuits, which include body conditioning, so I think I'm doing it right, but I'd really like to know what I'm doing to my body!

Pleae help!!

melaniecheeks

My trainer posted something thought provoking on Facebook yesterday:

Steady state cardio burns fuel, resistance burns fat.

I think understanding what source your body gets its energy from is quite complicated!

amyy902

hay im a PT and im also doing a degree in these sports sciencey topics.... well in simple youre on the right track, calories are a measure on energy, we get this and store it from our foods. when we exercise we tend to draw our first call of energy from carbs and use up that store first, once thats done we take from our fat stores, then when we have finished all that we take from our protein stores. which yes if this happens and thats the only place left to draw energy from then you will get muscle wastage but thats extreme cases.

in short this would happen if you didnt eat enough and didnt do any exercise either. thats is a very superficial overview simply explained. hope that helps!!

Azdak

It can get complicated and most people spend way too much time focusing on the details.

Stick with a basic, reasonable macronutrient ratio for your eating plan, focus on maintaining a negative energy (calorie) balance, and exercise as much for fitness as for weight loss. You don't need to know much more than that.

1. Your body is always using a combination of fuels--at rest and during exercise. The ratio changes according to the demands of the activity. You cannot "trick" your body or "force" it to use one specific fuel type (e.g. fats). The body does not use one type of fuel "first" and then switch to another type after a set period of time.

2. The fuel substrate (i.e. fat, carbohydrate, protein) utilized during a workout session has almost no long-term effect on stored body fat. Even if it did, the difference between exercising at a "fat burning" intensity vs a higher intensity would only be a few grams of fat--hardly even noticeable.

3. What happens in your body during a workout does not occur separately from what happens in your body the other 23 hours in the day. Again, even if you do a workout that "burns more fat", your body tends to respond by burning less fat the rest of the day (and vice versa), so that, after 24 hours, there is no difference in the percentage or actual amount of fat oxidized between a "fat burning" workout and a "non fat-burning" workout.

From a practical standpoint, the only thing you should be worrying about is maintaining a consistent calorie deficit. Train to improve your fitness. The exercise methods that make you fit and healthy -- doing a variety of cardio, lifting weights--also help you lose weight.

Azdak

hay im a PT and im also doing a degree in these sports sciencey topics.... well in simple youre on the right track, calories are a measure on energy, we get this and store it from our foods. when we exercise we tend to draw our first call of energy from carbs and use up that store first, once thats done we take from our fat stores, then when we have finished all that we take from our protein stores. which yes if this happens and thats the only place left to draw energy from then you will get muscle wastage but thats extreme cases.

in short this would happen if you didnt eat enough and didnt do any exercise either. thats is a very superficial overview simply explained. hope that helps!!

It's so extreme that bringing up the idea of "muscle wastage" is akin to raising fears about "asteroid strikes". Of all the bits of nonsensical fitness assertions out there, the idea that "cardio burns muscle" is one of the most ludicrous things I have heard in almost 30 years in this business.

MommaFuhrer

Interesting! I'd like to see more answers!

amyy902

hay im a PT and im also doing a degree in these sports sciencey topics.... well in simple youre on the right track, calories are a measure on energy, we get this and store it from our foods. when we exercise we tend to draw our first call of energy from carbs and use up that store first, once thats done we take from our fat stores, then when we have finished all that we take from our protein stores. which yes if this happens and thats the only place left to draw energy from then you will get muscle wastage but thats extreme cases.

in short this would happen if you didnt eat enough and didnt do any exercise either. thats is a very superficial overview simply explained. hope that helps!!

It's so extreme that bringing up the idea of "muscle wastage" is akin to raising fears about "asteroid strikes". Of all the bits of nonsensical fitness assertions out there, the idea that "cardio burns muscle" is one of the most ludicrous things I have heard in almost 30 years in this business.

yes and i noted it was in extreme cases, i myself have fallen victim to that. so it is a truth but its not going to happen to someone who is exercising and eating in a 'normal' manner.

Dayna154

bump

mixedfeelings

bump

Andaw

Thanks everyone, there have been some really useful posts here. I think I'm over-thinking things a bit too much but it's good to know that I'm pretty much doing ok.

I think the lesson here is to keep exercising to keep healthy and any fat-burning is a bonus!