Showing posts with label fat oxidation. Show all posts
Showing posts with label fat oxidation. Show all posts
Sunday, May 23, 2010
Weight Loss Ups your Power - if you're a competitive cyclist and not going nuts with the CR.
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There's been a debate for some time as to whether or not "fasted cardio" is ok. There's a "fasted cardio roundtable" at t-nation discussing this, and good arguments on either side. The title of a recent article made me think "great - a specific study on fasted cardio with elite athletes" Here's the title: "Effects of caloric restriction and overnight fasting on cycling endurance performance." But alas, it's not about fasted cardio: it's about doing an exertion test after ONE night of fasted cardio after having been on a calorie restricted diet.
Not the most usual circumstance. Indeed, the study is interesting nonetheless for a couple of other related reasons: it's looking at the effects on performance of a protocol often used by cyclists before competetive race season when they need to drop some weight to improve their Power to Weight Ratio (PWR) - lighter on the bike but still driving the same power means get there faster, if not fasted.
So not exactly fasted cardio - as in regularly doing cardio in a fasted state. But there are *some* findings that may reasonably be extended - maybe - around fasted cardio. In particular the effects shown around perceived exertion in this condition and intriguingly fat utilization.
Here's the abstract
Here's the actual protocol during the study:
In the lab: the athletes did a submaximal two hour endurance ride (with ipods and music of their choice if they wished) on lab bikes set up just like their racing bikes with the following condition:
Results:
over the 25 days of their CR, they lost weight - in particular their body fat dropped but their lean mass was maintained. They had a 1.7 plus or minus. 5kg body weight loss, with a drop in bf% of 2.1 (plus or minus .4) %. Lean mass increased by 2.1%. No muscle mass loss. That's a plus of exercise while doing calorie reduction: lean mass hangs in.
in the lab: the fasted, post CR test showed no statisitcal difference in power output, Vo2max, resting metabolic rate (RMR), revolutions per minute. In otherwords, nothing performance wise changed - in particular, nothing changed netgatively - as a result of the CR and fasted state of the test.
One place there was a difference: PWR at 90 and 100% vo2max was significantly different post CR (it went up), though no PLWR (power to lean weight ratio) changes.
The authors suggest:
Two notable changes/surprises: first, that perceived exertion was LOWER after the CR period. And second, that despite doing a heavy work load after an 11 hour fast, fat oxidation (using fat as the main fuel for the workout) did not change from baseline. Now me, i must be missing something because both base line test and re-test post CR were the same: post 11 hour fast. But here's what the authors say about the fat oxidation non-change:
Practical Applications
The authors have some cautiously positive effects to report
In other words, there's some good results in terms of body comp and PWR from a pretty intense caloric restriction for three weeks, but we don't know what would happen if this was strung out or for that matter repeated at intervals anywhere into competetive season. This ain't a license to go nuts.
And it's also not much help when thinking about fasted cardio as a regular practice.What i'm not sure this study says is what the authors state in the abstract: that "Caloric restriction (up to 40% for 3 weeks) and exercising after fasting overnight can improve a cyclist's PWR without compromising endurance cycling performance" Caloric restriction for three weeks with regular workouts, sure, but one session of fasted endurance work? Maybe i'm reading this wrong, but that seems a bit of a stretch. All it seems one can say is that after three weeks of caloric restriction, a sub max endurance workout in a fasted state when done by elite athletes doesn't have any negative effects - on them.
On the plus side: one can work to weigh less and maintain power, thereby increasing power. And for sports, like life, where better body comp has a host of benefits, a three week nutritionally balanced calorie cut with maintained workouts - at least for seasoned athletes - can be effective. Does this approach transfer to non-competetive athletes? May be worth investigating.
Citations
Related Articles
There's been a debate for some time as to whether or not "fasted cardio" is ok. There's a "fasted cardio roundtable" at t-nation discussing this, and good arguments on either side. The title of a recent article made me think "great - a specific study on fasted cardio with elite athletes" Here's the title: "Effects of caloric restriction and overnight fasting on cycling endurance performance." But alas, it's not about fasted cardio: it's about doing an exertion test after ONE night of fasted cardio after having been on a calorie restricted diet.Not the most usual circumstance. Indeed, the study is interesting nonetheless for a couple of other related reasons: it's looking at the effects on performance of a protocol often used by cyclists before competetive race season when they need to drop some weight to improve their Power to Weight Ratio (PWR) - lighter on the bike but still driving the same power means get there faster, if not fasted.
So not exactly fasted cardio - as in regularly doing cardio in a fasted state. But there are *some* findings that may reasonably be extended - maybe - around fasted cardio. In particular the effects shown around perceived exertion in this condition and intriguingly fat utilization.
Here's the abstract
Doesn't the above sound to you like the cyclists were doing both caloric restriction for three weeks AND doing fasted cardio at the same time? Well it turns out the only time we know that they did fasted cardio was on two test occaisions: before the diet started and at the end of the three week period
J Strength Cond Res. 2009 Mar;23(2):560-70.
Effects of caloric restriction and overnight fasting on cycling endurance performance.
Ferguson LM, Rossi KA, Ward E, Jadwin E, Miller TA, Miller WC.
Department of Exercise Science, The George Washington University, Washington, DC, USA. Abstract:
In addition to aerobic endurance and anaerobic capacity, high power-to-weight ratio (PWR) is important for cycling performance. Cyclists often try to lose weight before race season to improve body composition and optimize PWR. Research has demonstrated body fat-reducing benefits of exercise after fasting overnight. We hypothesized that fasted-state exercise in calorie-restricted trained cyclists would not result in performance decrements and that their PWR would improve significantly. We also hypothesized that substrate use during fasted-state submaximal endurance cycling would shift to greater reliance on fat. Ten trained, competitive cyclists completed a protocol consisting of baseline testing, 3 weeks of caloric restriction (CR), and post-CR testing. The testing sessions measured pre- and post-CR values for resting metabolic rate (RMR), body composition, VO2, PWR and power-to-lean weight ratio (PLWR), and power output, as well as 2-hour submaximal cycling performance, rating of perceived exertion (RPE), and respiratory exchange ratio (RER). There were no significant differences between baseline and post-CR for submaximal trial RER, power output, VO2, RMR, VO2max, or workload at VO2max. However, RPE was significantly lower, and PWR was significantly higher post-CR, whereas RER did not change. The cyclists' PWR and body composition improved significantly, and their overall weight, fat weight, and body fat percentage decreased. Lean mass was maintained. The cyclists' RPE decreased significantly during 2 hours of submaximal cycling post-CR, and there was no decrement in submaximal or maximal cycling performance after 3 weeks of CR combined with overnight fasting. Caloric restriction (up to 40% for 3 weeks) and exercising after fasting overnight can improve a cyclist's PWR without compromising endurance cycling performance.
Here's the actual protocol during the study:
For the CR period, subjects followed a fixed-macronutrient, calorie-restricted diet [this was set carbs, fats, proteins equivalent to a 40% reduction in total calories -mc] while maintaining their normal exercise training routines. None of the athletes were actively involved in strength training. Individual training plans typically involved base miles and some interval work, as it was still the off-season. Training was not standardized among athletes, because each athlete was a seasoned cyclist, accustomed to his or her own training regimen, and making changes to those plans could have produced chronic fatigue, muscle soreness, or altered the training volume to which each cyclist was accustomed-any of which could have led to unfavorable temporary adaptations that would have confounded their performance in their paired time trials.In other words, they were doing big calorie restriction and that's the only change to their training. We don't know if training actually changed in any way during this period - though participants were asked to keep things the same during the study as before in terms of these workouts. Ok, let's say that's all fine, then.
In the lab: the athletes did a submaximal two hour endurance ride (with ipods and music of their choice if they wished) on lab bikes set up just like their racing bikes with the following condition:
A metronome was used to ensure that subjects cycled at a constant 50 rpm to allow for consistent evaluation of workload. Subjects warmed up for 5 minutes at 100 W for men and 75Wfor women. The workload was incrementally increased by 50 Wevery 2.5 minutes. When HR reached 35 bpm below age-predicted maximal HR (220 bpm 2 age), or when the respiratory quotient exceeded 1, the workload was only increased by 25 Wevery 2.5 minutes until exhaustion. The subject cycled to exhaustion, ending the test voluntarily when he or she could no longer pedal or keep the 50-rpm cadence. Each subject wore a mouthpiece and nose clip, and ventilatory air was continuously analyzed forO2 consumption and CO2 production using the ParvoMedics system. Also, HR, RPE, and power output were recorded at the end of each stage throughout the test.
Results:
over the 25 days of their CR, they lost weight - in particular their body fat dropped but their lean mass was maintained. They had a 1.7 plus or minus. 5kg body weight loss, with a drop in bf% of 2.1 (plus or minus .4) %. Lean mass increased by 2.1%. No muscle mass loss. That's a plus of exercise while doing calorie reduction: lean mass hangs in.
in the lab: the fasted, post CR test showed no statisitcal difference in power output, Vo2max, resting metabolic rate (RMR), revolutions per minute. In otherwords, nothing performance wise changed - in particular, nothing changed netgatively - as a result of the CR and fasted state of the test.
One place there was a difference: PWR at 90 and 100% vo2max was significantly different post CR (it went up), though no PLWR (power to lean weight ratio) changes.
The authors suggest:
The increase in PWR was influenced by the significant decreases in body weight and percent body fat. Because there was no significant loss of lean body mass, the PLWRwas maintained. Thus, power was maintained not simply because of weight loss but because of the maintenance of fat-free mass. This increase in power output at high intensity levels, accompanied by a decrease in body weight, will provide the cyclist with more energy and power for improved uphill cycling performance.Overall then, the cyclists did get what they wanted: an improved Power to Weight Ratio: their power stays the same, but at a lighter weight. That translates potentially into getting the bike moving down the road faster.
Two notable changes/surprises: first, that perceived exertion was LOWER after the CR period. And second, that despite doing a heavy work load after an 11 hour fast, fat oxidation (using fat as the main fuel for the workout) did not change from baseline. Now me, i must be missing something because both base line test and re-test post CR were the same: post 11 hour fast. But here's what the authors say about the fat oxidation non-change:
Although we hypothesized that we would find a greater reliance on fat oxidation post-CR, particularly because RER [respiratory exchange rate - seeing which fuel is used more, carbs or fat -mc] - measuring has been previously shown to be lower in the fasted state (Aragón-Vargas LF 93, Knapik JJ88 ), this was not statistically supported. ...A possible explanation for the lack of a significant shift to fat metabolism is that the subjects were all highly trained endurance cyclists already and, as such, were able to use fat as a fuel more efficiently than if they had been untrained subjects.Hmm. Makes ya wonder.
Practical Applications
The authors have some cautiously positive effects to report
[The study results] suggests that CR (up to 40% for 3 weeks) and exercising after fasting overnight can improve a cyclist’s PWR without compromising endurance cycling performance. Furthermore, this study demonstrates that a shortterm period of moderately severe CR is not detrimental to the conditioning process. Athletes can continue to prepare for the upcoming race season in terms of endurance training while dieting to reduce body weight without losing significant muscle mass in the process. However, it is not known what would happen to performance if an athlete were to prolong his or her exposure to the CR beyond 3 weeks, or to repeat the 3-week exposure to CR with short intervals of balanced energy intake in between. The current data suggest that a protocol such as the one outlined in this report would be most appropriate if used in the off-season to increase PWR or during the season before a competition.
In other words, there's some good results in terms of body comp and PWR from a pretty intense caloric restriction for three weeks, but we don't know what would happen if this was strung out or for that matter repeated at intervals anywhere into competetive season. This ain't a license to go nuts.
And it's also not much help when thinking about fasted cardio as a regular practice.What i'm not sure this study says is what the authors state in the abstract: that "Caloric restriction (up to 40% for 3 weeks) and exercising after fasting overnight can improve a cyclist's PWR without compromising endurance cycling performance" Caloric restriction for three weeks with regular workouts, sure, but one session of fasted endurance work? Maybe i'm reading this wrong, but that seems a bit of a stretch. All it seems one can say is that after three weeks of caloric restriction, a sub max endurance workout in a fasted state when done by elite athletes doesn't have any negative effects - on them.
On the plus side: one can work to weigh less and maintain power, thereby increasing power. And for sports, like life, where better body comp has a host of benefits, a three week nutritionally balanced calorie cut with maintained workouts - at least for seasoned athletes - can be effective. Does this approach transfer to non-competetive athletes? May be worth investigating.
Citations
Ferguson LM, Rossi KA, Ward E, Jadwin E, Miller TA, & Miller WC (2009). Effects of caloric restriction and overnight fasting on cycling endurance performance. Journal of strength and conditioning research / National Strength & Conditioning Association, 23 (2), 560-70 PMID: 19197210
Aragón-Vargas LF (1993). Effects of fasting on endurance exercise. Sports medicine (Auckland, N.Z.), 16 (4), 255-65 PMID: 8248683
Knapik JJ, Meredith CN, Jones BH, Suek L, Young VR, & Evans WJ (1988). Influence of fasting on carbohydrate and fat metabolism during rest and exercise in men. Journal of applied physiology (Bethesda, Md. : 1985), 64 (5), 1923-9 PMID: 3292504
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- Cardio levels when ya can't do HIIT
- HIIT intervals (on bikes) for fat loss
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- Respect the Fat
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Friday, August 7, 2009
Respect the Fat: An overview of Fat Burning Goodness
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We hear it all the time: fat is bad; we have too much; we need to shed the fat. Yes sure, leaner is better for health. But that doesn't mean either that fat is bad or that ingesting the right kinds of fats (yup, there are kinds) is bad. Quite the opposite.
In fact, fat is our biggest and one might argue most versatile sources of fuel. It also makes up the shell of every cell in our body, and is part of a host of other essential for life processes that happen inside us. But the focus of this post is on how fat contributes to providing us with the fuel we need and use in every breath we take.
Fat is amazing. It's the most abundant fuel source in the
body.
Every time we breath we're using fat to help take care of the energy needs of our bodies, whether thats muscular activity of lifting something, or the chemical activity of digesting something, or the transport activity of moving something from one cell to another.
In each of these cases, Fat contributes the lion's share of the energy to our physical processes. We couldn't live without it: adipose tissue affords protection to our body's various systems as well as immediate fuel storage sources; the membranes of cells are part fat and enable standard operations of the heart and lungs to get nutrients throughout our systems. And, it's also an energy reserve. Like having a bunch of batteries in the cupboard ready for when the smoke alarm or flashlight fails. Swap out the old cells put in the new.
Despite these great capacities, most of us want to shed some extra weight. Indeed, we know that it's our incredible ability to store fuel resources that works to our socio-cultural detriment in a society where fuel-as-food is readily and cheaply abundant. We put on extra weight. We carry reserves in excess of what we need given the ready abundance of fuel around us. And there are some pretty nasty health costs to carrying around that much surplus fuel, too. Type II diebetes, metabolic syndrome, additional load on joints, etc.
And so we look for ways to burn it off.
The goal of this article is to take a 50thousand foot view (ie really simplified view) at part of what's going on with that burn off, and why therefore fat is our super fuel and seemingly super nemesis.
What i mean by simplified view? Here's a map of the metabolic process:
A metabolic map, indicating the reactions of intermediary metabolism and the enzymes that catalyze them. Over 500 different chemical intermediates, or metabolites, and a greater number of enzymes are represented here. ((c) 1997 20th edition, designed by and courtesy of D. E. Nicholson, University of Leeds , U. K., and the Sigma Chemical Co. )
We're considering a wee fraction of this entire process, and only part of what's going on as illustrated below (source):
The three stages of catabolism. Stage I: Proteins, polysaccharides, and lipids are broken down into their component building blocks, which are relatively few in number. Stage II: The various building blocks are degraded into the common product, the acetyl groups of acetyl-CoA. Stage III: Catabolism converges to three principal end products: water, carbon dioxide, and ammonia
These maps help to get that this is complex cool stuff. we are amazing. The above maps let us ask the question - how do we get the good stuff out of fat to use? and to appreciate how a little bit of fat goes a really really long way. To get to that, we need to consider what energy from fat means. And that means taking a look at ATP, the primal fuel block (what fat and other nutrients in large part become), and also situating fat a bit relative to other nutrients like carbs and protein in this fuel-making process (nothing shines out like a comparison). We'll take a wee look at what can increase the fat burn in cells (mitochondria) and finally, where this should lead: why fat, while it burns all the time, is still a challenge to shed.
Energy from Fat
Anyone who's spent time counting calories likely knows that the standard wisdom about calories is that carbs are 4kcal per gram and so is protein. Fat however is 9kcal per gram. Remember a calorie is a measurement of energy: the amount of energy to raise 1 g of water 1 degree.
Right from the outset, it looks like fat has the advantage in providing us with more energy than either carbs or protein. Looks like about twice as much. That's true. But what is really cool about fat is that it gives us more useable fuel for the body to do its lifting, chemical processing and transporting than we get from protein or carbs, and that's in terms of it's translation from a fat to ATP.
ATP
ATP or adenosine triphosphate. ATP is what powers all the energy in cells.
We hear a lot about ATP in the body building world and general strength training: in big lifts the point of that long recovery is to replenish phosphocreatine stores that can make a little bit of ATP available without the presence of oxygen - like when we hold our breath, or exhale out, to do that big dead lift, or keep our head under water for that 50m sprint to the end of the pool. 1 molecule of phosophocreatine when it's broken down into ATP yields only a few ATP molecules. That's not a lot for intense work, but it can re-synthesize quickly for short 30sec bursts.
But what about for efforts that last longer than 30secs? Then we start getting into carb and fat world. Protein is used for very little energy - 2-5% - it has other jobs. If no other source of fuel is available for energy - no carbs say after a workout and you use protein - a chunk of that protein will be used as fuel - transformed into carb-like fuel for replenishing energy stores. And when folks take on more protein than can be used for any current physical requirements, protein will be translated into fat.
Digression on Protein and Starvation
Here's the other thing about Protein as fuel: some folks find that when they're working out and dieting at the same time, it seems their fat loss stalls out. That's a well-studied phenomena that if the body has fat for fuel, and it feels like it's being starved (only recieving 50% or more of the needed cals for maintenance), it will horde fat for as long as possible, and will start to catabolize (break down) other sources in our bodies for fuel. Protein from muscle is a goody.
So often folks starting an exercise program after they've started dieting need to INCREASE their calories a bit to off set starvation.
Now if someone persists at starvation levels long enough, the weight will come off. The famous Minnesota experiment demonstrated this action.
So back to ATP - and ATP from our nutrients.
The body stores only 80-100g of ATP at a time. So it has to synthesize ATP all the time.
A huge point of taking in food is to convert these fuels into ATP. Without going into the detail here, here's where fat comes into its own: a molecule of glucose (stuff from carbs generally), depending on the source, produces 36 or 38 molecules of ATP. 1 fatty acid molecule (derived from fat sources) produces 460 molecules of ATP. That's considerably more than 10 times the amount of usable fuel for muscular, chemical and transport activities than carbs.
Why is this? Basically the way fat breaks down more of it can be translated into ATP than carbs. If you look at the second big map above, you'll see that carbs have to go through three intermediate steps before they get to acetlyCoA. Fat can go pretty much directly to that stage.
Fewer steps, less stuff used for other things than ATP...
The process of how these various translations of a food into a bundle of energy occurs is really cool. It's a testament to how adaptable we are. For instance if we don't have enough carbs in our bodies for the jobs carbs are used to do - like feed our brains and liver - the body will translate fat into carb substitute. This process is the subject of books like Lyle McDonald's excellent review called the Ketogenic Diet.
Why bother with carbs at all if Fat is so awesome? and is that the secret of these "low carb" diets?
Fat burns in the flame of carbohydrate.
One of the best ways to stoke fat to burn is in the presence of carbs - this has to do with stuff in the Citric Acid Cycle. When carbs aren't present and the body has to go ketogenic to use fats instead, well, it can do it, but it's not necessarily optimal. You can skip this next bit if you wish but some folks have asked for a bit more explanation of what this Flame means. So the following digression:
And fat in something called "slow glycolosis" (part of the Krebs Cycle, pictured as the ring in the second figure above) loves carbs to let it burn baby burn. Now before anyone jumps on me, no Fat does not REQUIRE carbs to help it break down into the stuff that enters the KC to become ATP but it is sort of the path of least resistance, perhaps, if i can put it that way.
And just to repeat what may well be obvious to all:
fat burns as fuel via the happily fairly constant activity of breathing. Fat is "oxidized" to break
down into fuel. This oxidation takes place in the mitochondria of the cell. Hence it's important to have rather a lot of it as we breath so much.
Aside: Fat Burners. We may also recall that the discussion last week about super intense low volume 6min. workouts a week created as many new mitochondrias (ie fat burners) as did 1-2 hours a week of steady state cardio. Want to enhance fat burning? combined with diet, enhancing mitochondira helps.
I dunno, just thinking about all the things a bit of fat does it once again strikes me how incredibly amazing we are. So versatile. We can fuel ourselves up with just about anything we ingest. Our systems have preferences but can adapt to circumstances. Wild.
And fat is wild because it does so much for us.
Losing/Burning Fat - Hard Homeostatic or Hard Habit?
But you may be asking if we're burning fat (converting it into ATP pretty much constantly), why are we Fat? Why is fat hard to lose?
I guess the question might be reframed as is fat hard to lose?
What is hard, it seems, when food is so easily available to us, in ways historically unprecedented, we follow our ancient wiring and we eat. We want to load up for the lean times. But we don't live in scarcity. Access to ready prepared food continues to increase. Our need for these responses to horde up are less appropriate.
see
So perhaps what's hard is the habits around caloric restriction: being patient enough with ourselves to learn new habits to support some caloric restriction to lose weight. To be patient with ourselves that fat loss takes time. While the inital excess fat may come off faster, those last ten pounds are killers, and there are reasons for this too that i've discussed elsewhere.
And without habits to support ongoing lean attitudes, then how do we keep the weight coming off? and then how do we maintain our goal weight?
I've said it before, its this need for habits around food rather than specific diets that i like precision nutrition. It supports habits.
Rewiring for Fat: Love your Fat; Burn your Fat; Respect the Fat
So while we are wired to grab store and horde fuel, we can adapt our behaviours to be lean in the face of abundance. Once we start turning on those habits, we do need to tune them to optimize fat burning. The basic part of fat burning is to get the balance of eat less right with whatever activity one is at, so one stays productively above starvation level.
Being patient with ourselves to learn what that sweet spot mix of caloric restriction and workout effort to optimize fat burning - if that's the priority - takes time, patience, and a strategy to be able to assess if what's being tried works. Again, i'll say i like precision nutrition becuase it has a method called an Individualization Guide to support exactly that process.
Calorie Note: Why only 3500kcals to drop a Pound of Fat?
Some folks have noticed a seeming discrepancy between cals in a pound of fat and that there are fewer calories to burn a pound of "fat"
I'm still looking for sources on this, but here's the argument: let's start with the basics.
1g of fat = 9kcal
so 1kg of fat =9000kcal
9000/2.2 = 4091kcal / pound of fat (1kg/2.2=1lb)
Apparently a pound of human fat is made up of 10% water + 5% other materials that aren't digested - i need sources to support this, but if we go with that for a moment
4091 -15%= 3477.35
That's approx 3500kcals.
One other frequently quoted statement on the web is "Human fat tissue contains about 87% lipids, so that 1 kg of body-fat tissue has roughly the caloric energy of 870 g of pure fat, or 7800 kcal."
- just put that quote into google and it will show up on a dozen sites - but no primary source for it. - still that conveniently gets to the well cited 3500kcal/lb of (human) fat.
The closest i have to a real source for such info is
Higher Up and Further In
if you're intersted in going deeper into the physiology here, may i recommend
Exercise Physiology: Energy, Nutrition, and Human Performance, 6th Ed.
McArdle, Katch & Katch (US| UK)
There's a 7th ed coming in November 09.
If you get really intrigued, for after the above, there's Brook's bioenergetics, referenced in the side bar book recommendations
Related Posts
In fact, fat is our biggest and one might argue most versatile sources of fuel. It also makes up the shell of every cell in our body, and is part of a host of other essential for life processes that happen inside us. But the focus of this post is on how fat contributes to providing us with the fuel we need and use in every breath we take.
Fat is amazing. It's the most abundant fuel source in the
body.Every time we breath we're using fat to help take care of the energy needs of our bodies, whether thats muscular activity of lifting something, or the chemical activity of digesting something, or the transport activity of moving something from one cell to another.
In each of these cases, Fat contributes the lion's share of the energy to our physical processes. We couldn't live without it: adipose tissue affords protection to our body's various systems as well as immediate fuel storage sources; the membranes of cells are part fat and enable standard operations of the heart and lungs to get nutrients throughout our systems. And, it's also an energy reserve. Like having a bunch of batteries in the cupboard ready for when the smoke alarm or flashlight fails. Swap out the old cells put in the new.
Despite these great capacities, most of us want to shed some extra weight. Indeed, we know that it's our incredible ability to store fuel resources that works to our socio-cultural detriment in a society where fuel-as-food is readily and cheaply abundant. We put on extra weight. We carry reserves in excess of what we need given the ready abundance of fuel around us. And there are some pretty nasty health costs to carrying around that much surplus fuel, too. Type II diebetes, metabolic syndrome, additional load on joints, etc.
And so we look for ways to burn it off.
The goal of this article is to take a 50thousand foot view (ie really simplified view) at part of what's going on with that burn off, and why therefore fat is our super fuel and seemingly super nemesis.
What i mean by simplified view? Here's a map of the metabolic process:
A metabolic map, indicating the reactions of intermediary metabolism and the enzymes that catalyze them. Over 500 different chemical intermediates, or metabolites, and a greater number of enzymes are represented here. ((c) 1997 20th edition, designed by and courtesy of D. E. Nicholson, We're considering a wee fraction of this entire process, and only part of what's going on as illustrated below (source):
The three stages of catabolism. Stage I: Proteins, polysaccharides, and lipids are broken down into their component building blocks, which are relatively few in number. Stage II: The various building blocks are degraded into the common product, the acetyl groups of acetyl-CoA. Stage III: Catabolism converges to three principal end products: water, carbon dioxide, and ammoniaThese maps help to get that this is complex cool stuff. we are amazing. The above maps let us ask the question - how do we get the good stuff out of fat to use? and to appreciate how a little bit of fat goes a really really long way. To get to that, we need to consider what energy from fat means. And that means taking a look at ATP, the primal fuel block (what fat and other nutrients in large part become), and also situating fat a bit relative to other nutrients like carbs and protein in this fuel-making process (nothing shines out like a comparison). We'll take a wee look at what can increase the fat burn in cells (mitochondria) and finally, where this should lead: why fat, while it burns all the time, is still a challenge to shed.
Energy from Fat
Anyone who's spent time counting calories likely knows that the standard wisdom about calories is that carbs are 4kcal per gram and so is protein. Fat however is 9kcal per gram. Remember a calorie is a measurement of energy: the amount of energy to raise 1 g of water 1 degree.
Right from the outset, it looks like fat has the advantage in providing us with more energy than either carbs or protein. Looks like about twice as much. That's true. But what is really cool about fat is that it gives us more useable fuel for the body to do its lifting, chemical processing and transporting than we get from protein or carbs, and that's in terms of it's translation from a fat to ATP.
ATP
ATP or adenosine triphosphate. ATP is what powers all the energy in cells.
We hear a lot about ATP in the body building world and general strength training: in big lifts the point of that long recovery is to replenish phosphocreatine stores that can make a little bit of ATP available without the presence of oxygen - like when we hold our breath, or exhale out, to do that big dead lift, or keep our head under water for that 50m sprint to the end of the pool. 1 molecule of phosophocreatine when it's broken down into ATP yields only a few ATP molecules. That's not a lot for intense work, but it can re-synthesize quickly for short 30sec bursts.
But what about for efforts that last longer than 30secs? Then we start getting into carb and fat world. Protein is used for very little energy - 2-5% - it has other jobs. If no other source of fuel is available for energy - no carbs say after a workout and you use protein - a chunk of that protein will be used as fuel - transformed into carb-like fuel for replenishing energy stores. And when folks take on more protein than can be used for any current physical requirements, protein will be translated into fat.
Digression on Protein and Starvation
Here's the other thing about Protein as fuel: some folks find that when they're working out and dieting at the same time, it seems their fat loss stalls out. That's a well-studied phenomena that if the body has fat for fuel, and it feels like it's being starved (only recieving 50% or more of the needed cals for maintenance), it will horde fat for as long as possible, and will start to catabolize (break down) other sources in our bodies for fuel. Protein from muscle is a goody.
So often folks starting an exercise program after they've started dieting need to INCREASE their calories a bit to off set starvation.
Now if someone persists at starvation levels long enough, the weight will come off. The famous Minnesota experiment demonstrated this action.
So back to ATP - and ATP from our nutrients.
The body stores only 80-100g of ATP at a time. So it has to synthesize ATP all the time.
A huge point of taking in food is to convert these fuels into ATP. Without going into the detail here, here's where fat comes into its own: a molecule of glucose (stuff from carbs generally), depending on the source, produces 36 or 38 molecules of ATP. 1 fatty acid molecule (derived from fat sources) produces 460 molecules of ATP. That's considerably more than 10 times the amount of usable fuel for muscular, chemical and transport activities than carbs.
Why is this? Basically the way fat breaks down more of it can be translated into ATP than carbs. If you look at the second big map above, you'll see that carbs have to go through three intermediate steps before they get to acetlyCoA. Fat can go pretty much directly to that stage.
Fewer steps, less stuff used for other things than ATP...
The process of how these various translations of a food into a bundle of energy occurs is really cool. It's a testament to how adaptable we are. For instance if we don't have enough carbs in our bodies for the jobs carbs are used to do - like feed our brains and liver - the body will translate fat into carb substitute. This process is the subject of books like Lyle McDonald's excellent review called the Ketogenic Diet.
Why bother with carbs at all if Fat is so awesome? and is that the secret of these "low carb" diets?
Fat burns in the flame of carbohydrate.
One of the best ways to stoke fat to burn is in the presence of carbs - this has to do with stuff in the Citric Acid Cycle. When carbs aren't present and the body has to go ketogenic to use fats instead, well, it can do it, but it's not necessarily optimal. You can skip this next bit if you wish but some folks have asked for a bit more explanation of what this Flame means. So the following digression:
Always on, All the time - when possibleAnd just a note: that even diets that cut out grains and other what we might call fast carbs (fast to become avilable as fuel) to go ketogenic, even here one is encouraged to eat veggies. Lots of them. Why? carbs are part of our natural metabolic process. A third of our energy comes from carbs. Our brains like carbs. Our fat burning engine likes carbs; our muscles like carbs. In balance.
remember that all our energy systems are in play pretty much all the time. There's a little bit of glycolysis (carb burning) happening along with beta-oxidation (fat burning) even when we're at rest.
a by-product of the whole carb burning process is oxaloacetate (OOA). It connects with Acetyl-CoA to form citrate, and that gets processed in the citric acid cycle and ATP is produced.
Duel types of fat
Now here's the cool thing. Fat is so versatile it can get used as fuel a couple of ways. One of these - that produces the MOST ATP is via getting it into the citric acid cycle (see diagram above). This is what FFA's - free fatty acids do. Fat also becomes available as fuel as Glycerol. When you're low on carbs, it's glycerol that gets used as carbs (via gluconeogenisis) - whether you're doing a heavy workout or doing a ketogenic diet. BUT a molecule of glycerol only produces 19 ATP molecules.
FFA's Rock
Compare this rate of ATP availability with what FFA's do when they can enter the krebs cycle. Without getting into the Krebs cycle, fat conversion is also a relatively slow process so that pathway won't get energy to the muscles super quick. Which partially explains why even if you're on a ketogenic diet, most folks recommend getting some carbs into your system prior to a workout in particular for better available energy - and fat utilization. Now this is not to say that we don't adapt in a ketogenic situation to get the turnover of fat into carb substitute happening faster, and when loads are reasonable, all could feel ok. But even so, that rate can't compete with FFA going through the citric acid cycle.
Fuel from FFA is FFA going into Citric Acid Cycle (burning in the flame of carb)
first step is beta-oxidation of a FFA: cleaving off a couple of carbons from the fat (see first image by the battery) and we get products NADH and FADH2 which can form up into acetylCoA which can hook up with OOA to do the citric acid dance. This cycle in turn breaks down the acetylCoA into co2 and H. The H come out of the citric acid cycle to oxidize via something called phosphorylation. The result is 460 ATP from FFA conversion to energy.
SO this is why fat burns and really BURNS up in the flame of carbohydrate.
And fat in something called "slow glycolosis" (part of the Krebs Cycle, pictured as the ring in the second figure above) loves carbs to let it burn baby burn. Now before anyone jumps on me, no Fat does not REQUIRE carbs to help it break down into the stuff that enters the KC to become ATP but it is sort of the path of least resistance, perhaps, if i can put it that way.
And just to repeat what may well be obvious to all:
fat burns as fuel via the happily fairly constant activity of breathing. Fat is "oxidized" to break
down into fuel. This oxidation takes place in the mitochondria of the cell. Hence it's important to have rather a lot of it as we breath so much.Aside: Fat Burners. We may also recall that the discussion last week about super intense low volume 6min. workouts a week created as many new mitochondrias (ie fat burners) as did 1-2 hours a week of steady state cardio. Want to enhance fat burning? combined with diet, enhancing mitochondira helps.
I dunno, just thinking about all the things a bit of fat does it once again strikes me how incredibly amazing we are. So versatile. We can fuel ourselves up with just about anything we ingest. Our systems have preferences but can adapt to circumstances. Wild.
And fat is wild because it does so much for us.
Losing/Burning Fat - Hard Homeostatic or Hard Habit?
But you may be asking if we're burning fat (converting it into ATP pretty much constantly), why are we Fat? Why is fat hard to lose?
I guess the question might be reframed as is fat hard to lose?
What is hard, it seems, when food is so easily available to us, in ways historically unprecedented, we follow our ancient wiring and we eat. We want to load up for the lean times. But we don't live in scarcity. Access to ready prepared food continues to increase. Our need for these responses to horde up are less appropriate.
see
Hays NP and Roberts SB. Aspects of Eating Behaviors "Disinhibition" and "Restraint" Are Related to Weight Gain and BMI in Women. Obesity 2008:16, 52–58. doi:10.1038/oby.2007.12.
So perhaps what's hard is the habits around caloric restriction: being patient enough with ourselves to learn new habits to support some caloric restriction to lose weight. To be patient with ourselves that fat loss takes time. While the inital excess fat may come off faster, those last ten pounds are killers, and there are reasons for this too that i've discussed elsewhere.
And without habits to support ongoing lean attitudes, then how do we keep the weight coming off? and then how do we maintain our goal weight?
I've said it before, its this need for habits around food rather than specific diets that i like precision nutrition. It supports habits.
Rewiring for Fat: Love your Fat; Burn your Fat; Respect the Fat
So while we are wired to grab store and horde fuel, we can adapt our behaviours to be lean in the face of abundance. Once we start turning on those habits, we do need to tune them to optimize fat burning. The basic part of fat burning is to get the balance of eat less right with whatever activity one is at, so one stays productively above starvation level.
Being patient with ourselves to learn what that sweet spot mix of caloric restriction and workout effort to optimize fat burning - if that's the priority - takes time, patience, and a strategy to be able to assess if what's being tried works. Again, i'll say i like precision nutrition becuase it has a method called an Individualization Guide to support exactly that process.
Calorie Note: Why only 3500kcals to drop a Pound of Fat?
Some folks have noticed a seeming discrepancy between cals in a pound of fat and that there are fewer calories to burn a pound of "fat"
I'm still looking for sources on this, but here's the argument: let's start with the basics.
1g of fat = 9kcal
so 1kg of fat =9000kcal
9000/2.2 = 4091kcal / pound of fat (1kg/2.2=1lb)
Apparently a pound of human fat is made up of 10% water + 5% other materials that aren't digested - i need sources to support this, but if we go with that for a moment
4091 -15%= 3477.35
That's approx 3500kcals.
One other frequently quoted statement on the web is "Human fat tissue contains about 87% lipids, so that 1 kg of body-fat tissue has roughly the caloric energy of 870 g of pure fat, or 7800 kcal."
- just put that quote into google and it will show up on a dozen sites - but no primary source for it. - still that conveniently gets to the well cited 3500kcal/lb of (human) fat.
The closest i have to a real source for such info is
Adipose tissue contains 82-88% fat, 2-2.6% protein, and 10-14% water. The energy yield of adipose tissue is 8000-9000 kcal (34-38 MJ) per kg or 3600-4000 kcal (15.1-16.8 MJ) per pound.and that's at Answers.com, and i've no idea who writes this stuff for them or from where they get it.
Higher Up and Further In
if you're intersted in going deeper into the physiology here, may i recommend
Exercise Physiology: Energy, Nutrition, and Human Performance, 6th Ed.
McArdle, Katch & Katch (US| UK)
There's a 7th ed coming in November 09.
If you get really intrigued, for after the above, there's Brook's bioenergetics, referenced in the side bar book recommendations
Related Posts
- getting off diets and onto better eating habits. change is pain: reduce the pain :)
- becoming a better burner: 6mins a week to trigger mitochondrial growth = to 4.5 hours cardio
- cardio with kettlebells
- vo2max effort training
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