Nutrient Partitioning - The role of body fat % !
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What if our bodies could become a machine that converts everything you eat into muscles, while each time you try to shred, it would only be those fat cells? Now, this could be quite a hypothetical goal to achieve as we do not live in such ideal conditions where every calorie we eat would fill up the muscle glycogen, whereas, every time we lose, it would be those adipose tissues. In a nutshell, nutrient partitioning means where the calories go (muscle or fat tissues) when you overeat them, while where does it come from (muscle or fat tissue) when you eat less. So, there must be something controlling this calorie partitioning, right? * There is a very small percentage under our scope, as the amount of muscle mass we gain or lose is largely defined by our genetics and adherence to training. * Apart from the exercises, the hormonal levels play an important role in this complex process. Having a good testosterone level would contribute to the muscle building process, while a high amount of cortisols can counter this. (Ref1). Our genetics play a major role in maintaining an optimal level for these hormones including thyroid hormones as well as the nervous system. * Having said that, there are two more essential correlated factors controlling energy storage, the insulin and the body fat %. * Individuals with a high amount of skeletal insulin sensitivity will tend to store a large amount of calories in glycogen stores inside muscle cells, while the ones with poor sensitivity will tend to store more in fat cells. (Remember, insulin is a storage hormone that helps transport the nutrients to liver, muscle and fat cells). * Individuals with higher body fat % tend to carry and lose more fats while dieting (shredding). On the other hand, you tend to lose more muscles when you carry less fat %. This is one of the major reasons why it’s important to maintain a certain amount of protein while shredding(Ref 2, 3). * However, this is just reversed in case of the individuals who are naturally lean(lesser body fat %), as they simply gain more muscle even when overfed, while the fatter individuals tend to gain more fat than muscle mass while overfeeding. (Ref 2, 3) (I know you might be able to relate the different body types here). Here comes the role of leptins (released primarily by fat cells). The level of leptins denotes the amount of fat in our body. * The more fats we have, the higher the levels of leptins. * Every time you go on a fat loss diet, the leptin levels drop to a certain level. On the contrary to a refeed, it tends to rise up. * Leptin is an indicator of the glucose levels in the fat stores. Now, when the body fat % rises regularly – leptin levels also increase. Overeating or consuming excess calories continuously can lead to impairment of this signal that indicates the leptin levels to the brain, further resulting in leptin resistance. * So now your brain thinks you are starving as it is not getting the correct measure of leptin while your body’s fat levels continue to rise. With time, this leads to the impaired glucose uptake to the cells. To simplify it: the fatter you are (higher body fat %), the more body fat is available as a fuel source but also your body has a tendency to store the extra energy in your fat cells. The risk of developing insulin resistance and leptin resistance are both high. This is not a good condition for fat loss regardless of your genetics. Similarly, the leaner you are (less body fat %), the lesser body fat is available as a fuel source (it’s always good to keep having an adequate/minimal protein while dieting). Additionally, your body tends to move extra calories into your muscle glycogen. Finally, the leaner you are, the more insulin sensitive you become. The final question- how do we improve this partitioning? * Rather than blaming genetics, involving ourselves into physical activities and exercises , especially strength training can be helpful in improving the glucose uptake into your muscle cells, leading to better nutrition partitioning. * In summary, when we define an individual as endomorph, ectomorph or mesomorph, apart from the genes, it’s the result of current body fat percentage and the insulin doing their job, which can be improved with constant effort and time. References: Ref 1: A Kamba, et al. Association between Higher Serum Cortisol Levels and Decreased Insulin Secretion in a General Population. PLoS One. 2016; 11(11): e0166077 Ref 2: H Sagayama, et al. Measurement of body composition in response to a short period of overfeeding. J Physiol Anthropol. 2014; 33(1): 29 Ref 3: A Leaf, J Antonio. The Effects of Overfeeding on Body Composition: The Role of Macronutrient Composition – A Narrative Review. Int J Exerc Sci. 2017; 10(8): 1275–1296.