| Article Summary: As you become leaner your body will become more sensitive to insulin as a result.
 Of the macronutrients, fats are the best source of energy the body can receive.
 Your body actually needs very few carbohydrates to function properly day-to-day.
 
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Insulin Sensitivity: 
Why You Can't Blast That Fat For Good!
 Have you ever wondered why, after all the  exercise and healthy eating you do, you still can't shift that last bit  of fat? You hit the gym four to five times a week or more, you even try  to get a run in over the weekend and on top of this you're eating all  the healthiest food you can find; despite this your still not super lean  like you want to be. I have the answer to your nightmare - Insulin sensitivity. 
Insulin sensitivity will eventually replace  the term "weight loss" and "fat loss" as the new hot topic. Insulin has a  powerful ability to prevent fat breakdown by its anabolic (rebuilding)  properties.  
Few health and fitness professionals know or  understand Insulin sensitivity (IS) which is why its no wonder that the  every day man or woman is finding weight and fat so difficult to lose;  it's incredibly hard to win against an obstacle you don't know is there!   
Let me explain Insulin's role and how it's  sensitivity changes depending upon how close you are to your weight and  fat loss goals.
 
Have you ever wondered why, after all the  exercise and healthy eating you do, you still can't shift that last bit  of fat? You hit the gym four to five times a week or more, you even try  to get a run in over the weekend and on top of this you're eating all  the healthiest food you can find; despite this your still not super lean  like you want to be. I have the answer to your nightmare - Insulin sensitivity. 
Insulin sensitivity will eventually replace  the term "weight loss" and "fat loss" as the new hot topic. Insulin has a  powerful ability to prevent fat breakdown by its anabolic (rebuilding)  properties.  
Few health and fitness professionals know or  understand Insulin sensitivity (IS) which is why its no wonder that the  every day man or woman is finding weight and fat so difficult to lose;  it's incredibly hard to win against an obstacle you don't know is there!   
Let me explain Insulin's role and how it's  sensitivity changes depending upon how close you are to your weight and  fat loss goals.  
  
 
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It's Incredibly Difficult To Win Against
An Obstacle You Don't Know Is There.  
Insulin Sensitivity:
 
 
 You might remember the hormone Insulin from  articles referring to muscle gains due to its anabolic properties. Well  further research into Insulin action shows that these same anabolic  tendencies also affect the fat cells1. What most people don't realize is, Insulin also targets the fat, liver, and muscle cells when it is released1. This is not the only problem, though. 
 A review of the research tells us that IS is actually increased when you lower your weight or body fat percentage2,3,11.  It's also important to note that IS gets stronger the more you work  out. The catabolic effect of exercise increases IS during a work out and  for about 30-45 minutes post workout3.  
 This means as a healthy exercising individual you simply can't eat the same amount of carbohydrate food that you did before and expect to keep getting better results.    It's important to note that Insulin is sensitive to both carbohydrate and protein consumed, but not fat4. However, of all the food sources, it's the higher carbohydrate meals that elevate Insulin levels the most after a meal5. (See diagram below and look at lunchtime reading.) 
 Even though there are individual differences  to IS levels depending upon your metabolic type, the evidence strongly  suggests that the leaner and lighter you become the stronger your IS  levels will be. This means carbohydrates (and protein  to a lesser extent) are producing a bigger and more powerful anabolic  effect the closer you get to your weight loss/body fat goals.     
 
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It's The Higher Carbohydrate Meals That
Elevate Insulin Levels The Most After A Meal.  
Self-Preservation:
 
 
 It seems the body has a way to protect the  ever reducing mass of itself as it gets smaller and smaller by ramping  up its IS. It also protects itself from too much exercise induced  catabolism by making you more IS around your workouts. Why does the body  do this, you might ask? This is a good question, but the body has a  very good answer: protection and survival. 
 Imagine the scenario - a body that could  just keep losing weight without any self checking system! "Heaven!" I  hear you say, that is until you realize that this body would be in  danger of wasting itself away. If your body was without any anabolic or  rebuilding effect, critical tissues, such as connective ligaments and  tendon absorption would occur, muscle wasting would be uncontrolled and  shutting down of vital systems in the body would happen next.  
 If the body could be in a constant state of  catabolism the body could break itself down into an unrecoverable state!  Constant catabolism isn't just limited to energy sources either, being  dangerously low on certain nutrients could mean you might leech them  from an eye or a section of nerve tissue or other vital organs and body  parts.  
 There is more and more evidence to suggest  the body already performs such processes as these as we see osteoporosis  and varying degree's of vision in people as well as an array of bone  and joint problems, to name but a few.  
 The evidence is out there to suggest the body leeches nutrients from other parts of itself if it is not obtained from the diet6,7,12.  Without a rebuilding response from the body, it would be unable to get  bigger and stronger or recover properly from exercise and stress. This  is why Insulin is so important and so is a variable rate of IS. 
  
 
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The Body Will Leech Nutrients From Other Organs
As Neccessary Evidenced By Varying Degree's Of Vision.  
Insulin's Role:
 
 
 Insulin's role is protective of the whole so  that body parts can rebuild and maintain integrity of internal systems  as well as keep energy stores at an optimum and safe level.  
 Insulin and IS is a very good protection  system, but like all systems it can be manipulated, you just have to  know how. IS is a pre-programmed mechanism responding to the amount and  sweetness of the carbohydrates (carbs) that we eat.  
 Everybody has a unique set IS level which is  governed by many internal factors that can be measured by determining  your metabolic type4. Despite some people having a lower IS  level and a slower Insulin response who are better adapted to eating  carbs in their diet, there is still a vast majority of people out there  struggling to get to their fat and weight loss goals from having high  levels of IS and strong Insulin responses.  
 What this really means though, is not that  our bodies have become stubborn fat burners, it's that even the  healthiest of food available today is still a little too high in carbs  for most of us. Your IS is really highlighting that your current food is  still a bit too refined and sweet for your needs.  
  
 
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Insulin Sensitivity Is Mechanism Which Responds
To The Amount And Sweetness Of Carbs We Eat.  
Carbohydrate Usage:
 
 
 You can appreciate this a lot more when you  realize that there are eight essential amino acids and eight essential  fatty acids required for life. These same nutrients are used all over  the body for normal and constant metabolic processes such as repair of  hair, skin, bone, muscle, red blood cells. Fat is used for energy  purposes, protein only in ketosis.  
 Compare this to carbs, which have a very  limited role around the body, in fact it's only the brain that needs  carbohydrates as a fuel source, most cellular processes are happy using  fat. That's one of the reasons why we are designed to carry so much of  it around with us.  
 Carbs do provide us with fiber and minuscule  but essential amounts of vitamins and minerals which are very difficult  to store (unless they're fat soluble), and if they're not used at that  time, they are passed through the body very quickly6.  
 This means the main role of carbs is to top  up the liver and muscles which are not as big a store as some people  would realize. A closer look at the anatomy of a person reveals that the  human liver can hold approx 80-100g of carbohydrates and the muscles  can only hold 1-2% of carbs by volume, known as glycogen.  
  
 
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It's Only The Brain That Needs
Carbohydrates As A Fuel Source In The Body.  
Glycogen Storage
 
 
 The exact amount of how much glycogen you  can store is dependent upon how much muscle mass you have and how  intense your training. Individuals need more carbs if they train at  higher levels of intensity as the main fuel used is glucose. This is why  there is a greater storage effect after this type of training, called  supercompensation7.  
 It's a long conversion to find the muscle  volume of a person and then work out 1-2% of that volume and finally  convert that volume to mass. But if you take an average of 1.5% storage  capacity for muscle glycogen and then work out a range of muscle mass  (in this case men) from the literature at 38.4kg for distance runners  and 58.7kg for bodybuilders8, then glycogen storage capacity is only 97-150g from my calculations. 
 Add on the liver store of 80-100g and you  are looking at total capacity of 177 - 250g of carbohydrates that the  body can realistically store (Women should use the small figure as an  accurate reflection of what glycogen stores they can hold.). This is not  a lot of carb intake per day if you consider we are, or should be,  using fat as a fuel source for most of the day for most of our bodily  processes and never get to a point of complete depletion. 
  | Athlete | Muscle Mass | Muscle Glycogen Storage | Combined Glycogen Storage | 
  | Distance Runner | 38.4kg | 97g | 177g | 
  | Bodybuilder | 58.7kg | 150g | 250g | 

Fat Usage:
 
 
 I'm sure nobody really likes fat,  but I have to say it's an incredibly powerful fuel source. Very little  fat can provide energy for extensive periods. It is reported that 3%  body fat is enough energy for someone to run 2 consecutive marathons  together8.    Quite clearly we are built to run on fat and  use carbs sparingly, otherwise our anatomy would be completely  different and be built the other way around, meaning small fat deposits  in our livers and muscles with plenty of carbs built around us.  
 A good analogy would be - why build a car  with a tiny fuel tank? It would make sense to design a car with a much  bigger fuel tank and a richer fuel supply that was at least twice the  energy capacity of most fuel without any extra weight: 
 Fat = 9 Cals per gram, Carbs and Protein = 4.2 Cals per gram 
 A much more intelligent design would be to  store the most potent fuel in an unlimited area and then add the idea of  a turbo charger that could boost performance temporarily for stressful  or strenuous circumstances for a perfectly designed machine. This  smaller reserve for high octane fuel would be the intake for carbs which  are limited to storage in the liver and muscles as they are required in  the least amount, with the main fuel of fat stored all over.  
  
 
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It Is Reported That 3% Body Fat Is Enough Energy For
Someone To Run Two Consecutive Marathons Together.  
Rethinking Your Diet:
 
 
 A rethink of your diet might be in order if  you do eat root vegetables and fruits whilst also consuming bread, dairy  and/or cereals. Be weary of so called "healthy" fruit juices as these  are really sugared water. This is also true of the new trendy flavored  waters that you can buy these days, these products and most sauces are  easy ways to alter your carb/fat/protein intake and can be a leading  culprit in contributing to your weight and fat gain. 
 This is why "healthy" people are often  "lean" people. I see evidence of this all the time with my own clients,  not just in the research literature. I'm sure you have seen people who  train all the time but don't control their diet very well, they try to  think in terms of calories in versus calories out only, with little or  no regard for the carbohydrate intake.    I have to say I don't see their bodies change a lot, where as there are other people who eat cleaner food, they eat some raw vegetables,  they cook most of their food at home and avoid heavily processed foods  with added chemicals including - colorings, preservatives, artificial  flavors etc and there bodies reflect this. They don't come in the gym  and have to workout hard, they are workingout smart using tighter  control of their food.    We all know it's much easier to take the  calories in during a blow out, than it is to work them off in the gym.  In fact its practically impossible to get really lean and stay there  unless you're healthy first. Fitness will only work for so long before  your body will be unable to maintain the exertion and catabolism  induced.  
  
 
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Those People Who Eat Cleaner Food Don't Have
To Workout Hard They Can Workout Smart.  
Potential Hazards From Caloric Deficit:
 
 
 If you do not provide your body with  adequate nutritional support, you'll start witnessing sickness and run  down symptoms from poor recovery from your training sessions. If you  ignore this and continue, you will see problems with joints and bones or  both and you may also start to see symptoms in the muscular and  hormonal systems6,7,13.  
 This leeching of nutrients from other body  parts or other systems will only serve to weaken the whole - You! This  makes it harder and harder to have the energy to work out regularly and  keep the body in a healthy state where all systems are working  synergistically to utilize fat metabolism.    Stress hormones from a stressed system use  more glucose than fat and increase the need for stimulants and sugars  that are not going to serve you well in the long run due to your higher  sugar diet and your Insulin response. 
 Leeching of nutrients is another good reason  to clean up your diet and stick to vegetable and some fruit based  carbs. Scavenging necessary ingredients from other body parts is not a  long term survival method; we should be always aiming to eat foods that  revitalize our bodies, rather than our mouths. 
 If the body is without certain nutrients it  has to choose between switching off certain processes temporarily or  leeching what's needed from somewhere else in the body. This would mean  further catabolism/ breakdown when you are already in a catabolic state  from dieting and training. This puts a lot of stress on the body by  asking it to provide further breakdown in another area to sustain  itself, which is just more stress added to the system.  
 Now it's easy to see why the body might  prefer to go into a complex preservation mode and preferentially start  storing more energy as fat and break down the muscles as it is trying to  "save" itself rather than allowing constant catabolism. 
  
 
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We Should Be Always Aiming To Eat Foods That
Revitalize Our Bodies, Rather Than Our Mouths.  
Lack Of Need For Carbohydrates:
 
 
 I also studied the research on how much  depletion our livers receive overnight due to heavy brain activity  during our sleep cycle. It was reported that only approx 27 - 30 grams  of carbs overnight was used10. This is not a great deal of  carbohydrate food when you consider what people regularly consume at the  first meal of breakfast, never mind the rest of the day's intake.  
 Unless strenuous exercise or long periods of  mental focus are applied you are simply not built to consume too much  carbohydrate. Most people are simply burning a hole in their liver and  muscles when they exercise by going hard and then replace it with their  diet afterward. This means they are maintaining they're weight and fat  loss at best! 
 These are the people who as soon as they  stop exercising just balloon in size and weight as they can no longer  store the carbs internally as we all know that once the liver and  muscles reach full capacity the extra carbs are converted to fat.  Unfortunately most carbohydrate foods we see are extremely low in  nutrition, but their low cost and short preparation time make them very  convenient to everyone.  
 Thus, avoiding these at all costs is a must  if you're serious about getting the healthy body and lean definition you  see in fitness magazines. Some fruits and all vegetables are a much  better source of carbohydrates as they contain 1000's of nutrients and  phytochemicals compared to breads, cereals and pasta11.  
 A study I read recently described an apple  as having 10,000 to 15,000 nutrients contained within it versus  virtually none in a doughnut11.  
 Taking a metabolic type assessment will help  you sensibly reduce your carb intake and accurately determine which  nutrients you need the most from the various fruits and vegetables as  well as the sources that best suit your genetics for the 8 essential  amino acids and 8 essential fatty acids that are vital to healthy  functioning. 
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                                                                                                    Insulin is one of the body's most  anabolic muscle-building hormones. More specifically, it's a hormone  released by the pancreas in response to nutrient availability. Learn how  this amazing natural hormone can promote muscle gain!                                                                                                                                          We know that for athletes to  optimize their performance and be successful, they must consume  efficient amounts of nutrients from carbohydrates... Here are a few  facts and tips about carb loading, its importance, who benefits, and  more.                                                                            Bibliography:                                                              Taking in carbohydrates in the  post-workout period has long been seen as an essential component of your  muscle-building regimen. As I research though, it seems that  post-workout carbs will have no impact.                                       
 http://en.wikipedia.org/wiki/InsulinAge (Dordr). 2009 Nov 11. [Epub ahead of print] Fontana L, Klein S,  Holloszy JO. Effects of long-term calorie restriction and endurance  exercise on glucose tolerance, insulin action, and adipokine production.Gregory D. Cartee; Katsuhiko Funai; Exercise and Insulin:  Convergence or Divergence at AS160 and TBC1D1? Exerc Sport Sci Rev.  2009;37(4):188-195.http://en.wikipedia.org/wiki/Insulin#Synthesis.2C_physiological_effects.2C_and_degradationhttp://upload.wikimedia.org/wikipedia/commons/9/92/Suckale08_fig3_glucose_insulin_day.jpgWilliam L. Wolcott & Trish Fahey. 2002. The metabolic typing diet: Broadway booksPrice, Weston A. June 2003. Nutrition and Physical Degeneration. Keats Pub; 6th editionSpenst LF, Martin AD, Drinkwater DT. Muscle mass of competitive male athletes. J Sports Sci. 1993 Feb;11(1):3-8.Wardlow, G.M., and Insel, P.M. 1995. The water soluble vitamins. In: Perspectives in Nutrition. 3rd edition.LM Burke, B Kiens, JL Ivy. 2004. Carbohydrates and fat for training and recovery. Journal of Sports SciencesPaul Taylor. 2008. Food Comparison: Apple vs doughnut. ptonthenet.com contentFerrannini E. Physiological and metabolic consequences of obesity. 1995 Sep;44(9 Suppl 3):15-7. MetabolismThe Truth about Junk Food & Fast Food, Clinical Nutrition - YouTube Lecture Series. http://www.youtube.com/watch?v=PDw_SFGCzGE&feature=related
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