Exercise! - When you burn fat, where does it go?

04-09-2003, 12:49 PM
OK, really dumb question and I hope this is the right forum to ask...when you burn fat, where does it actually go? I know that once blood sugar levels stabalize the body reabsorbs fat back into the bloodstream and passes it on for processing. But where does it go from there and, once processed, how does it actualy get out of the body?

I've been doing Web searches and have found some basic anatomy information but nothing in great detail. A few texts have said that the fats are passed to the muscles and burned and others have said that it's passed on to the liver for filtering. But then what? Does anyone have a URL for an in-depth description of the process?

I guess the real question is...which hole does it come out of? :o My assumption would be that it is excreted in urine due to the fact that the fat is being filtered from the bloodstream...but I just want to make sure.

04-09-2003, 01:20 PM
You got it! It's in your pee. Here's the deal-o though you have to drink enough water for full processing to occur otherwise it will be redeposited somewhere else!

Miss Chris

04-09-2003, 01:23 PM
Originally posted by rochemist
You got it! It's in your pee. Here's the deal-o though you have to drink enough water for full processing to occur otherwise it will be redeposited somewhere else!

OK, that's exactly what I thought...so I've been pushing half a gallon to a gallon of water through my system each day. :D

04-15-2003, 01:01 PM
I've never thought of this. Off to drink even more water.

04-20-2003, 12:06 PM
I always thought they were just broken up and released as heat! Guess you learn something new everyday :D

04-23-2003, 09:01 AM
If I understand you question right you want to know how we actually lose weight?

Well this came up in my very first physiology lesson in my first degree course. The lecturer listed all of the options we gave him, many similar ideas to those already posted were given. The he asked the same question slightly differently "What is it we get rid of to lose weight? What is it that we don't put in that we do put out?"

Think about that. We drink in liquids and solids and we secrete them. The food we ingest has a thermic effect and we shed heat. Everything we ingest our body uses and gets rid of the excess and waste products. Thus keeping a balance of sorts. So how does fat get lost?

So what is left? He waited for 3 weeks before answering that question! The answer is in what you breath OUT - carbon monoxide.

It is a comparatively heavy molecule and is the body's way of geting rid of waste products not dealt with via the stomach. It also uses a comparatively large amount of kcals to expel it.

I am looking for the physiology 101 answer to this, but I seem to have loaned out the book to an undeserving student. But I am sure that the complete and simple answer is around here somewhere! When I find it I'll get back to you with the full explanation!


04-23-2003, 01:00 PM

You know, when a person does the low-carb diet, it's always suggested that he or she carries some breath mints because of the waste leaving the body as we breath out. I think both the urine suggestion and the breath suggestion make sense! Waste leaves our bodies in numerous ways, right?

This is not really on the subject, but do you still instruct your "Baggy-T's" class? If so, how's it going?


04-23-2003, 01:36 PM
Hi Cheryl,

Yes, you're right! And the Atkins stinky breath is caused by ketosis, take time out for the bit below and you'll be super informed if anyone around you tries a low carb diet. Scary isn't really the word, and this info doesn't expand the bit about the body using muscle and lean tissue as brain food. This effectively means EVERY other bit of your body can be targeted to be cannabalised!

As for the Baggy-T's I am now employed by a Neighbourhood project as a Healthy Living Worker. So I am into all sorts of health promotion events, smoking cessation, weight management, stress management etc etc etc. And guess what? I am manageing to get exercise into ALL OF THEM! SO it's all good fun, if exasperating and headachey!

I have to admit I am glad the newness is wearing off, I haven't ben on-line properly for ages.

Hope to read more of everyone soon, Stef.

"In diets that contain fewer than 900 calories, all food eaten including protein and fat is broken down into glucose to provide fuel for the body. Protein and fat are very expensive fuels for your body. You can only convert 70 percent of the protein and 30 percent of the fat you eat to glucose. The nitrogen from the protein is excreted in the urine. This leaves no protein for repair or maintenance of muscles and organs. Also, in diets containing fewer than 130 grams of carbohydrates, ketosis occurs and your body starts breaking down muscle and lean tissue to provide glucose for brain and nerve fuel. Your body's first need is for fuel. Your body's use of dietary fuels cannot be changed drastically by altering your diet.

Your body can and does take stored fat (as triglycerides) and incompletely breaks it down into ketones, which can be used as a fuel source for muscles and organs. To completely breakdown body fat, you need glucose and oxygen. If glucose is not available for fuel by your limiting dietary carbohydrates, your body learns to run on ketones, but your brain doesn't. Your brain gets sluggish because it only runs on glucose. Your body starts breaking down muscle and organ tissue to provide the needed glucose for brain tissue. Protein contains glucose in its structure and it can be scavenged for use by the brain and nerves. Quick weight loss diets claim they spare muscle protein, but they don't. A diet high in protein and low in carbohydrates does not spare muscle protein from being broken down, unless you eat enough carbohydrate. As you continue on a high protein, low carbohydrate diet, the amount of ketones increases and ketosis occurs. Ketones are very irritating to your kidneys and the kidneys try to get rid of the ketones through the urine."

04-26-2003, 03:22 AM
i thought that fat was stored "energy". when your body needs more fuel, or calories, it calls upon its fat stores and breaks the fat up into usable molecules. when we eat more calories than our bodies need, it is stored as fat. therefore, the only real way to lose fat will be to burn more calories than we consume so that our bodies have to dip into our fat supply.

i am in a stress/anxiety support group at school and i learned something interesting. we have always been told that stress is bad for you--blah, blah--but no one had ever given me a physiological reason why.

here is the passage form my handout:

the cells in our fat have a high turnover rate; they fill quickly when you overeat but they release fat easily too(liar, liar). during stress, the abdominal cells become more active. if the stress is exercise, the fat can be burned in the muscles.

but what if the stress is emotional? fat leaves the cells and travels through the bloodstream, but no muscle cells need the calories. so the fat ends up clinging to the artery walls. any kind of emotional stress releases fat, which showers the heart and

i thought this was pretty interesting. i hope this helped.