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Training & Nutrition Learn how to develop a training schedule that's good for you. What should you eat and drink on your ride? Learn everything you need to know about training and nutrition here.

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Old 06-26-12, 05:02 AM   #1
jim p
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How fast does the body convert extra calories to fat?

Lets say a person eats an extra 3500 calories on a particular day. Will these calories show up as an extra pound of fat in 1 hour, or 6 hours, or 1 day, or 1 week?

My weight will fluctuate 5 lbs per day just due to the weight of food and water that I consume. I don't think that I am metabolizing fat at these kinds of rates.
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Old 06-26-12, 05:33 AM   #2
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Lets say a person eats an extra 3500 calories on a particular day. Will these calories show up as an extra pound of fat in 1 hour, or 6 hours, or 1 day, or 1 week?

My weight will fluctuate 5 lbs per day just due to the weight of food and water that I consume. I don't think that I am metabolizing fat at these kinds of rates.
You'd be surprised. First call on food intake is to replenish glycogen stores. Once they are full (they will often fill very quickly in people who are inactive and/or overeat) the surplus calories begin to be stored as fat within minutes of hitting your bloodstream - which will take between a few minutes and a couple of hours after eating. See here.
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Old 06-26-12, 06:01 AM   #3
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Thanks for the link. That was some interesting information. It helps to explain how it is easy to gain weight but hard to lose the weight. Extra calories are quickly stored as fat and then the fat is the 3rd or 4th in line for energy use by the body. So unless you use up your first line energy sources you would never tap into your fat reserve.
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Old 06-26-12, 07:43 AM   #4
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You have it backwards. You use stored fat for low intensity effort. But when you do more intense effort, the energy from fat is not enough and you have to use your glycogen reserves.

It's easy to gain weight because it is easy in modern society to obtain excess food. If you had to run down an antelope instead of driving to Safeway and buying cheap government subsidized meat, you wouldn't be so concerned about being overweight.
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Old 06-26-12, 09:40 AM   #5
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Maybe I do have it backwards about which energy source is used first by the body but it would seem that glucose would be used first because it is already in the blood stream.

As far as cheap meat due to government subsidies, that doesn't work for me because I pay the taxes which the government uses to pay for these subsidies. I don't eat the store bought meat so I just totally lose on that deal. I am a member of the kill it, butcher it, cook it, and eat it club.
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Old 06-26-12, 12:04 PM   #6
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You'd be surprised. First call on food intake is to replenish glycogen stores. Once they are full (they will often fill very quickly in people who are inactive and/or overeat) the surplus calories begin to be stored as fat within minutes of hitting your bloodstream - which will take between a few minutes and a couple of hours after eating. See here.
As a big double century approaches, I've been reading more about the pre-ride eating.

Nancy Clark's "Sports Nutrition Guidebook" (which doesn't seem to espouse anything off the wall and seems even-keeled about nutrition) says regarding fuel before morning workouts "Most people get good results from 0.5 gram of carbohydrate per pound of body weight one hour before moderately hard exercise, or 2 grams of carbohydrate per pound ... four hours beforehand."

Normally I'd just eat a regular meal the night before, and a couple hundred calories (slice or two of toast, Gatorade or Starbucks Double Shot) on the drive to the ride. I'll be starting at 3:30am though, and expect to be out for 18+ hours. I'll consume 250-300kcal/hr during the ride, but would I benefit from eating ~1600kcal (in my case) at 11:30pm the night before? That's a lot of food. I anticipate I'll be well fed throughout the day on Friday (and in these couple days leading up to it) and have no fear that my glycogen reserves wouldn't be close to topped off.
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Old 06-26-12, 12:17 PM   #7
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The answer really depends on your personal metabolism and the nutrition plan you use to deal with it. There are some people who handle carbs just fine (i.e. their blood sugar doesn't rise above 140 after a carb-laden meal), and they will metabolize carbs just fine. As long as their calories in more or less equal their calories out, they will be OK.

This is not the case if you can't metabolize carbs normally (diabetic, insulin resistant, etc.) In that case, your excess carbs will be converted into fat stores pretty rapidly. Not only that, but often your blood sugar will spike, causing you to be even more hungry a couple hours later. If you have blood sugar problems, just about the worst thing you can do is "carb load" before a ride or even during a ride.

I have blood sugar problems myself, and unless the ride is 45 miles or longer, don't have any carbs during the ride. On longer rides, I will consume around 250 calories an hour from a fruit & nut bar, containing around 28 carbs per bar. This works just fine, because those carbs are metabolized during the ride without any problems.

Making judgments about daily metabolism is a very iffy thing, no matter what your metabolism. The average male body is around 60% water, which means if you weight 180 lbs., 108 lbs. of that is water. Daily variations of 2 to 3% should just be considered "noise", mainly because of the high concentration of water in your body and all things that can affect that.

In other words, there is no one answer to your question, and certainly not an easy answer. If metabolism were that simple, we wouldn't have the problem with obesity that we do.
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Old 06-26-12, 12:27 PM   #8
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As a big double century approaches, I've been reading more about the pre-ride eating.

Nancy Clark's "Sports Nutrition Guidebook" (which doesn't seem to espouse anything off the wall and seems even-keeled about nutrition) says regarding fuel before morning workouts "Most people get good results from 0.5 gram of carbohydrate per pound of body weight one hour before moderately hard exercise, or 2 grams of carbohydrate per pound ... four hours beforehand."

Normally I'd just eat a regular meal the night before, and a couple hundred calories (slice or two of toast, Gatorade or Starbucks Double Shot) on the drive to the ride. I'll be starting at 3:30am though, and expect to be out for 18+ hours. I'll consume 250-300kcal/hr during the ride, but would I benefit from eating ~1600kcal (in my case) at 11:30pm the night before? That's a lot of food. I anticipate I'll be well fed throughout the day on Friday (and in these couple days leading up to it) and have no fear that my glycogen reserves wouldn't be close to topped off.
When I was starting to ride doubles, I'd wake up 3 hours before the ride and drink about 400 calories of what was essentially a recovery drink which was sitting in a cooler beside my bed, then go back to sleep. That works really well. Nothing else before the ride.

I think it's important to eat a good high carb meal the night before, but don't stuff yourself. I have a friend who swears by eating 3 hot dogs on buns. I prefer pasta. Rather than drink coffee just before the ride, I take a caffeine pill. Doesn't make me pee inconveniently early in the ride.
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Old 06-26-12, 01:38 PM   #9
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You'd be surprised. First call on food intake is to replenish glycogen stores. Once they are full (they will often fill very quickly in people who are inactive and/or overeat) the surplus calories begin to be stored as fat within minutes of hitting your bloodstream - which will take between a few minutes and a couple of hours after eating. See here.
This is not entirely accurate.

Yes, if your glycogen stores are saturated to begin with, you start seeing conversion of calories into fat right away. But, unless you're habitually on a high-carbohydrate hypercaloric diet, your stores are normally not saturated. Your stores can accommodate 3000 calories of glycogen before you start seeing conversion into fat.

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My weight will fluctuate 5 lbs per day just due to the weight of food and water that I consume. I don't think that I am metabolizing fat at these kinds of rates.
Weight fluctuations on this scale have almost nothing to do with fat. It's your hydration levels, contents of the GI tract, and glycogen. 3500 calories of fat is 1 pound, but 3500 calories of glycogen is as much as 6 pounds.
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Old 06-26-12, 01:57 PM   #10
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Maybe I do have it backwards about which energy source is used first by the body but it would seem that glucose would be used first because it is already in the blood stream.
Glucose is in your blood stream, and so is a little bit of fat ("free fatty acids"), and they are both continuously being used. Glucose accounts for most of the resting metabolism, and fat is the preferred fuel for your muscles. Only at high levels of exercise intensity, when muscles can't cope with the load by burning fat, they start tapping into glucose stores.

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Old 06-26-12, 07:02 PM   #11
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Thanks for the info. So muscles like to burn fat. This means that I have to keep pedaling.
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Old 06-26-12, 08:29 PM   #12
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Glucose accounts for most of the resting metabolism, and fat is the preferred fuel for your muscles. Only at high levels of exercise intensity, when muscles can't cope with the load by burning fat, they start tapping into glucose stores.
Close, but significant glycogen utilization starts at moderate intensity and dominates at high intensity.
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Old 06-27-12, 05:48 AM   #13
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I can't read the chart. Do you have a link that would be more readable.
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Old 06-27-12, 08:03 AM   #14
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I can't read the chart. Do you have a link that would be more readable.
Click on it. It's an attachment.
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Old 06-27-12, 11:40 AM   #15
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I can't read the chart. Do you have a link that would be more readable.
As CFB mentioned you can click on it or here is the complete paper: http://ju-st.in/best/be_thin_research.pdf
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Old 06-27-12, 03:04 PM   #16
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This information is hard to analyze for determining how to burn the most fat with the least effort. It looks like a maximum effort would always use the most energy from all sources but moderate effort might burn or convert fat to energy without using up so much of the other energy sources.

I know that just one day and one ride don't mean much but yesterday I decided to do my hill repeats very slowly. This morning when I weighed I was down a pound. I know that I can fluctuate 5 lbs so this weighing does not mean much. So I am going to go out and ride slowly again this afternoon and see what results if any I see tomorrow morning.

It would be nice to be able to burn fat and lose weight without having to ride myself into the ground.
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Old 06-27-12, 09:38 PM   #17
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It would be nice to be able to burn fat and lose weight without having to ride myself into the ground.
If you're trying to drop weight and you have the time, long rides at a moderate pace are very good. You burn more calories and I find the hunger pangs are not as bad. Fat burning is maximized at 65% of VO2Max which is a moderate intensity.
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Old 06-27-12, 10:32 PM   #18
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This information is hard to analyze for determining how to burn the most fat with the least effort. It looks like a maximum effort would always use the most energy from all sources but moderate effort might burn or convert fat to energy without using up so much of the other energy sources.

I know that just one day and one ride don't mean much but yesterday I decided to do my hill repeats very slowly. This morning when I weighed I was down a pound. I know that I can fluctuate 5 lbs so this weighing does not mean much. So I am going to go out and ride slowly again this afternoon and see what results if any I see tomorrow morning.

It would be nice to be able to burn fat and lose weight without having to ride myself into the ground.
The issue is that you can "ride yourself into the ground." When you get tired, you stop riding. End of program. So the object of the game is to ride as many hours/week as possible without getting wasted, which is going to mandate a moderate pace. 65% of VO2max, as mentioned by Greg, isn't a value that many people can relate to, however. That works out to be about 80% of max heart rate (MHR). In terms of effort, you'd be sweating pretty good, have a feeling of pushing fairly hard on the pedals, and be breathing deeply and faster than normal, but not breathing really hard. I'd say that's a little harder than you really want to go, because as I said, you'll wear out. Try dropping down to a pace where you are breathing deeply and sweating, but the pedaling seems fairly easy. You'll just have to experiment to find a pace where you can get in say, 10 hrs./week without wearing down. Most folks take every 4th week much more easily to give themselves a break. If you can burn 500 calories/hr. for 10 hours, that's 5000 calories. If we guess that you'll eat half or so of that back in extra food, you'd drop about 1/2 lb./week, just from riding. That's a good, sustainable pace which adds up over a few months. Once you get in better shape, you'll be able to up the intensity on a couple of those rides each week.
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Old 06-28-12, 05:51 AM   #19
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Again I know that this does not mean much, but today I was down 1/2 lb from yesterday. This gives me a little hope at losing the last few pounds. I had been stuck with no weight loss for about 2 months. I was just maintaining. I only need to lose 10.5 lbs to get to my ridiculous goal weight of 140 lbs. I am 6 feet tall so I am going to be pretty thin. I still have the fat layer around the stomach.

I am riding so easy that it feels like cheating. My heart rate on the climbs is 115 to 120 and I am not breathing very hard. My speed is around 5 mph. I usually ride for about 1 hour and 45 minutes. At this pace I can ride hungry and not feel like I am going to starve and after riding I don't feel like I need to eat everything is sight.

I will report back in a week and see if I am still losing weight. I started out at 200 lbs and lost 5 lbs per week until I decided to see if I could just maintain my weight. I maintained the weight for about 3 months and then decided that I wanted to lose some more weight at a slower rate. This is when I discovered that I was not able to lose anymore weight. Now I have hope again to drop on down.
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Old 06-28-12, 09:03 AM   #20
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Your goal weight sounds pretty lean for 6'. I'm not sure why you want to be so light unless you are planning to race. If so, I wouldn't give up completely on intensity or strength work or you'll risk losing power along with weight and your power/weight ratio won't improve. I don't know what your goals are but I would include at least one day a week of hard efforts or maybe some strength training.
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Old 07-06-12, 11:43 AM   #21
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I had lost down to 147 but one big meal put me back up to 149 this morning. So over all I am down 1.5 lbs for the week. This rate of loss will work great for me. I am really having to watch what I eat.

Thanks for all the information about how food supplies are used by the body.

I will be continuing the slow and sometimes mashing gears for my weight lose and hopefully a little power building for the legs.

I will let you know how the weight loss goes for next week. Just letting you guys know how things are going gives me a little incentive to do as good as I can.
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Old 07-16-12, 06:08 AM   #22
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Well I blew it.

On July 8 I decided that I would do a long ride for me. I ate a large meal of tri colored slaw and a can of chilli beans about one hour before the ride. I head out and ride 63 miles in 7 hours. During the ride I only drank water with no food. I never got hungry or felt weak except for just being tired at the end of the ride.

About one hour after the ride the hunger set in and would not go away for the next 3 days. I was eating around 3500 calories per day and my weight went up to 156 lbs. Finally the hunger diminished and I could stop eating so much. This morning I was back down to 150.5 lbs.

So it is back to slow easy rides and no more than 20 miles per day.

I am happy about doing my longest ride of 63 miles but not to happy about my weight gain. I consider this a great experiment. I may do another experiment later of eating like you should while riding and seeing if this creates an unmanageable hunger. But I think that I will hold off on any more experiments until I lose on down to my goal.
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Old 07-16-12, 07:27 AM   #23
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OP, sounds like you're obsessing quite a bit about what your scales are telling you; as long as you are fit and exercising regularly, you should probably not be too concerned with a five pound fluctuation in weight.

To come clean, I've seen those tendencies in myself for the past year or so - I fluctuate between 143 and 149 - and aside from just wanting to get rid of the middle-aged jelly around my waist-line, I really don't have a lot to worry about. I am more fit than 90% of the guys my age here in the Bacon Belt, and have to force myself to not worry too much about the fact that I do not now, nor will I ever, look like a Marvel Comics movie superhero...
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Old 07-16-12, 08:47 AM   #24
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I agree with you about being a good weight and feeling good. I have diabetes and there are studies that indicate that the less you weigh the easier it is to control the diabetes. So I am trying to get to the bottom of my normal BMI just to see how it will affect my blood sugars.

One study showed that if a type 2 diabetic goes on a 300 cal diet per day for a week that it can bring the blood sugars back into control. I don't think that I could limit my food intake that much but it is a thought in the back of my mind.
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Old 07-16-12, 10:14 AM   #25
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Travelerman is on the mark, don't check your weight more than once a week or you will get obsessive. I tracked it daily for a month on one occasion, and sometimes more than that, and the fluctuations are completely normal. Heck, my weight can actually vary by as much as 7lbs over the course of a single day. How much you eat (weight, not calorie wise), how much you drink, how much you sweat, etc. etc. all this will affect your weight much more on a day by day basis than simple fat gain/loss. And dont forget that if you are improving, you are probably building muscles, which can also add an extra 1 or so pounds per week. But that is a good weight gain you actually want.
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