sharptailhunter

So, I got into cycling (and running) to lose weight, more specifically to become lean. With that, here are some questions I'm trying to figure out:
1. How is adipose (fat) tissue decreased?
2. When is it burned... During or after exercise?
3. If it can be burned during exercise, what type of exercise burns it best?

I know that we all have a very personalized way of leaning up, what I'm afte are the fundamentals, things that I can wrap my brain around. So, feel free to discuss the Krebs cycle and all that jazz.

TurboTurtle

1- The body uses fat and carb for energy. If your intake of calories is less than what you burned, the body does not re-store as much fat as there was before.

2- Both, but it really doesn't matter for weight/fat loss. The body uses calories it needs and stores the rest. If you don't eat it, it won't store it.

3- You burn close to a constant amount (i.e. 200 Cal/hr) up to close to LT (or whatever term you want to use). The rest is carbs. The easier the workout the greater the percentage of fat. BUT, it doesn't matter. The harder (or longer) you work out the more calories you burn and the more fat/weight you will use.

Maybe I misinterpreted your questions, but it sounds as if you believe that burning fat, as opposed to carbs, results in more weight/fat loss. It doesn't. You burn calories depending on the time and intensity of your workout. When you add calories back (eat) the body replenishes the carbs it used and then stores all the rest as fat. If you eat less than you burned, you end up with less fat.

TF

ericm979

The advantage to longer less strenuous rides in the "fat burning zone" isn't that they burn more fat than more intense rides. As TT wrote, they burn less per hour. But you can do more hours so the overall amount of calories you can burn is greater. For example, I can go about an hour at a 800 cal/hr pace, then I am done for the day. But I can go for 8 hours at 500 cal/hr. (the numbers aren't exact but you get the idea).

So if I only had an hour to ride and considered only fat burning not rest or other training factors, an hour time trial would be the most efficient use of my time. But if I had more time, a longer ride at lower intensity would burn more calories.

The amount you burn from fat vs glycogen is immaterial for weight loss- whatever you use in glycogen will have to be made up from somewhere. If you eat less than you burned it'll be made up from body fat.

Enthalpic

When you exercise you use up energy supplies both from within the muscles themselves and from bloodstream. After exercise the muscles uptake carbs and free fatty acids from the bloodstream to recover. As the bloods supply of free fatty acids is consumed your adipose tissue (fat) dumps fatty acids into the blood to maintain balance.

If you eat a high fat meal, blood fatty acids levels rise, and your adipose tissue takes up fatty acids to keep the levels normal. If you overeat carbs your liver converts them into fat for later storage by the adipose tissue.

sharptailhunter

Thanks for all the replies. They all helped to clear it up for me. I had a basic understanding of it. I knew that the body used carbs, protein and fats for fuel. I didn't realize as Turbo mentioned that the body burns a certain amount of fat during exercise. So, that leads to another question: Is there a way to make your body burn more fat during exercise?

I ask because it seems that we all have a huge gas tank as far as fat is concerned. It seems that the energy from carbs is burned quickly. If we could get enough energy from buring fat during exercise, think of how much longer you could exercise.

Is that possible or am I totally wack-o?

JayhawKen

I think that is the purported objective of the various methods of low heart rate training, sometimes known as the Maffetone method. I think Mark Scott believed it led to dramatic improvements for him in his triathlon training. I'm not sure the method transfers very well to cycling, since hills have such an impact on intensity.

In fact, for me cycling seems like just one long series of interval workouts...

TurboTurtle

Not totally, no.

The answer to your question is by getteing stronger. You see by chart above that the amount of fat burned is based on percent of VO2Max. Raise your VO2Max and riding at the same power will be at a lower percentage of VO2Max= higher percentage of fat.

TF

sharptailhunter

Yah, like the ride tonight, tons o' rollers.

Based on that chart, it does appear that during the 25% of VO2 max, most of the energy is being fueled by fat and fatty components. Look at all the muscle glycogen that is being used with the higher (i.e. 85%) percent of VO2 max. So, I assume that after that higher VO2 max exercising, the muscles will be rather depleted of their glycogen stores. And, as pointed out earlier by Enthalpic, they will use "carbs and free fatty acids from the bloodstream to recover. As the bloods supply of free fatty acids is consumed your adipose tissue (fat) dumps fatty acids into the blood to maintain balance."

That leads to this question, what makes for a good recovery meal? More carbs vs protein or fats? How wise is it to not eat much at all so that the body has to use it already stored fat (adipose tissue) to replenish the muscles' glycogen stores?

Roody

Look at the charts that enthalpic posted to help you follow the discussion. The cells need glucose, the simplest sugar, for energy. But the body can metabolize or break down carbohydrates, fats and even protein to get that glucose. But the body seems to prefer to get the glucose in a certain order of preference, based on the speed of the different processes:

1. From glucose that's already in the cells--but that lasts only a few seconds of exercise.
2. From glucose that's already floating around in the blood. This will last for a few minutes.
3. From glycogen--a form of sugar stored in the muscle cells and in the liver. This will last for a couple hours or so.
4. From triglycerides in the blood-->free fatty acids.
5. From stored fat in adipose tissues. This can last for many hours or even days or weeks.
6. From protein in the cells. This ordinarily is the body's last resort and leads to ketosis.

Now all of these occur together when you exercise. 1 - 4 happen more in vigorous exercise because they're fast processes. 5 happens more in moderate exercise, especially endurance activities like cycling. 6 happens when you're hungry or starving.

However, it doesn't matter which you do as far as losing weight goes. As others have said, this is because when you rest, your body goes back to a state of equilibrium: Blood glucose and triglycerides go back up. Glycogen is replenished in the muscle and liver cells. If protein was broken down in 6, it's built back up (anabolic steroids help here).

Where does the energy come from for restoring equilibrium? It usually comes from the big meal you want to eat after a hard ride. If you don't eat enough, your body will use adipose fat to restore equilibrium, just as it did back in 5. That's what people mean when they say that you continue to burn fat after you exercise. IOW, to lose weight you not only have to exercise, you also have to eat less after you exercise. Your body does not want to do that--it would rather have the meal--and that's one reason it's so hard for some people's bodies to lose fat.

Roody

It's very wise if, like most of us, you're trying to lose fat. If you consume a big recovery meal, you won't lose much fat and you might even gain some. (I can easily exercise for 3 hours a day, 7 days a week, and still gain weight.)

It's not so wise if you're a professional cyclist or weightlifter who doesn't have much fat to lose. If you're very lean, the body will begin tearing down protein--mostly from the muscle cells--in order to produce glucose and glycogen. This is why training table meals and recovery drinks are so important to competing athletes who don't have much adipose tissue. (This is also one main reason that anabolic steroids are so useful to ripped athletes. Steroids greatly increse the speed at which the torn down protein is rebuilt.)

This is one fact that's often ignored. The needs of somewhat pudgy amateur athletes are very different from the needs of ripped professionals. The pros need all that recovery food (and maybe the steroids), but I sure don't need either one.

ottsville

Depends on your goals, workout, and how soon you will be riding again. For a ride of an hour or less, I would just eat normally unless you are doing a really hard strength type workout in which case I would make sure to get some lean protein and healthy fats. Rides of 1-2 hrs I try to get some immediate carbs in after the ride and then eat normally the rest of the day. For long rides, if you are eating for recovery and NOT trying to lose weight, you should shoot for 2g of carbs/kg in the first two hrs after riding.

This article has some basics. Experiment to find what works for you.

kuan

Word of caution here though. Roody, you do not mention that adipose fat does nothing to replenish glycogen supplies. You will still have to do that by ingesting carbohydrate.

Your body will use fat as called upon by the type and intensity of activity, not based upon a ratio of glucose/glycogen/FFA/triglycerides that is present in the bloodstream.

sharptailhunter

Are we certain of that? I was under the assumption that once all the blood's supply of glucose is used up then the muscles' glycogen stores would be replenished by other fuels, such as adipose tissue. Is that not correct?

Enthalpic

Fat can not be converted into glycogen. If you were on a very low carb diet the muscles would remain glycogen depleted. Fortunately, even with moderate carbohydrate consumption, there is sufficient carbs kicking around to replenish the muscles.

kuan

Unfortunately, fat does not even convert into anything. It gets ingested as fat, gets broken down into smaller units of fat, gets reconstituted by the liver as fat, gets stored as fat, and gets used as fat.

TurboTurtle

Does the glycogen stored in non-used muscles get used during exercise by the major use muscles? - TF

kuan

Not directly, but two things may happen. The body might use it to replenish depleted glycogen or it may just be used up for general purposes and not get replenished because the body is severly depleted elsewhere.

Enthalpic

Fats are used for a lot more than just energy and energy storage.

A few examples:
-Your cell walls are made of fat (Lipid membranes).
-Acetyl CoA is used to produce acetylcholine and cholesterol. The cholesterol then goes on to form many important compounds such as steroids and vitD
-The essential fatty acids are used to make many signaling molecules such as the eicosanoids, etc.

Fats are important!

sharptailhunter

Yes, I agree that some fat is good, jus tnot the quantity that I behold. It is coming off though. That's why I started this thread, I just wanted to know how it was coming off. So, it seems that in order to get rid of it, it had to be "burned" through exercise. This has been a great thread. I have actaully gained a better understanding of the importance of carbs. Before I was hoping that I could just replenish my energy needs during and after exercise with my nifty fat stores. Looks like it's not that simple.

Tabagas_Ru

Muscle does not contain the enzyme glucose-6-phosphatase (g6p) which is necessary to transport glucose into the blood stream. Only the liver and the kidneys contain g6p. This is why glycogen in muscles can't be used to regulate blood glucose, which it would need to do, to be used elsewhere in the body, since glycogen needs to be converted to glucose before it can be used for anything. Additionally glycogen can't be transported through the body.

Your muscles have a finite capacity for glycogen, so even when very little is used, very little if any will be replaced. Even at rest your muscles need and use energy, so eventually the glycogen stores will decrease, regardless.

Tabagas_Ru

Fat is not converted to glycogen directly but it contributes to it. The glycerol backbone of a triglyceride is used to create glucose by supplying carbon molecules, which can be converted to glucose that will contribute to the regulation of blood glucose levels. Some of that glucose may get stored as glycogen. Up to 8% of blood glucose originates from glycerol. This pathway is called glycerol gluconeogenesis. So even though the amount of glucose supplied is not great it still is a significant amount.

rankin116

So if I read this thread, do I earn some Biochem credits or something?

Great info all, thanks for sharing the knowledge.

ericgu

Trained athletes will burn a high percentage of fat at a given power output, so yes, you can increase the amount of fat you are burning.

ericgu

At the end of a ride that is a reasonable length - say 2 hours - you will have used up a fair amount of glycogen. You will likely have low blood sugar, but you won't be hungry initially because exercise suppresses your hunger.

Then, when that wears off, you may get very hungry and overeat.

I think not eating is a bad idea. Much better to a mix of carb/protein in your protein to start replenishing your stores and get your blood sugar up, and avoid the hunger. But it's not a lot - a few hundred calories.

ottsville

Wrong, for the reasons someday RN said and also because the body can create fat stores from excess ingestion of calories be they from carbs, protein, OR fat.