 Metabolism: anabolism (building up) and catabolism (breaking down); commonly used to refer to the breakdown of food and its conversion into energy. This conversion into energy is what we think of as “burning calories”, and each person has a different rate at which we do so. Each person is born with a certain metabolic rate, fast, slow, medium; so are we stuck with it? Or can we change it? *All nutritional and fitness info must be discussed with your doctor before any changes to diet or exercise regime are implemented. RMR Our Resting Metabolic Rate is how fast our body burns energy (calories) while we are resting, and there are formulas you can use to calculate it manually, however there are also online tools such as this one on bodybuilding.com that will at least give you an idea. As a most basic explanation it involves calculations of our height, weight, age and gender. Note that a true measure of your RMR would be to enter your lean muscle mass (by subtracting the weight of the fat on your body), so this will have an impact on the results. As muscle potentially uses more energy than fat, two people weighing the same but with different body fat % would yield different RMR’s. Our RMR will tell us how many calories we burn in a day while at rest; if we consume more calories than this they will be stored as fat, if we consume less, we will lose weight. There are some factors however that can affect how many calories we will burn while at rest. Exercise It goes without saying that any day we exercise we will burn more calories, so reasoning states that if we consume the same amount of extra calories we have used exercising, we will not lose weight. However, as we exercise our body uses up the glucose it has stored in our muscles, and the process of replacing it uses up extra energy (calories). In order gain the benefit of these extra calories you need to do the type of exercise that uses up the glycogen in your muscles; weight training and running (especially sprinting) use a lot of glycogen and will raise your RMR. Low intensity steady stead cardio doesn’t use up much of our glycogen stores so you will not benefit from this increase in RMR. Muscle mass As we exercise we also build our muscle mass. How much mass depends upon the type of exercise performed and to what intensity, as well our nutrition, in particular post-workout nutrition. As we build our muscle mass, our lean body mass increases - even if we are losing weight on the scale: fat loss, water weight etc. – so this will affect our RMR. How much it will raise our RMR is much debated, and it seems as though the claims that each pound of increased muscle will burn an extra 50-100 calories per day are not entirely accurate (read more). However, one thing is agreed upon, the more muscle mass we have, the more energy it will take post-workout for our muscles to recover and replenish its glycogen stores. Age When we are young, and growing, our metabolism remains high in order to keep up with this growth; however, around the time we hit age 25 our body is done all of its natural growing and our metabolism slows down. Some of this is simply due to our body’s vital functions slowing down, but some is also due to a decrease in lean body mass. Between the ages of 25 and 65 we can easily lose 5lbs of muscle every 10 years, creating a metabolic reduction of between 2-4% each year. By doing resistance training we can help maintain our muscle mass in order to combat this decrease in metabolism. Sleep When we were young, and carefree, we slept, well, like babies; as we get older and stress is more present in our lives, getting enough sleep can be difficult. Although sleep does not directly affect our RMR, lack of sleep alters our hormone levels. These hormones influence how much food we eat during the day, what kind of food we eat, as well as how much of it to store as fat.
However, if our stress level remains high during the day, cortisol does not lower enough by the time we go to bed and disturbs our sleep patterns. As we’ve seen, decreased sleep wreaks havoc on the hormones that help regulate appetite and fat storage, potentially causing weight gain. In addition, cortisol plays a role in protein metabolism that is actually catabolic (to breakdown) by nature; this means that it works to reduce protein synthesis and tissue growth (by lowering testosterone) thereby rendering our efforts to build muscle potentially null and void. If our cortisol remains constantly high it will work to safeguard our vital functions; it essentially tries to protect us by using our muscle mass to build up our fat stores, knowing that this way our body can remain self-sufficient for longer.
Crash diets “Crash diets” – below 1200 calories a day – have been shown in studies to actually lower your RMR. In effect, your body will adapt to the lower calorie level given to it with a “starvation response” and again works to safeguard all vital functions at the expense of non-vital organs, such as muscle. This calorie reduction is perceived as stress and your hormones will react accordingly, especially cortisol. Other hormones are also affected, including testosterone (which helps build and protect your muscles), ghrelin and leptin. If your goal is to lose weight, a gradual reduction in calories leading to a 1-2lb/week weight loss will not affect your RMR and is much more sustainable and beneficial in the long term. Read more about managing weight loss. Insulin sensitivity As discussed in my article Insulin: Friend or Foe? insulin plays an important role in our muscle growth and fat storage. Insulin is a hormone produced by the pancreas that is released as a response to the food we eat. When we eat food it gets broken down and sent to the liver where it is processed and converted into – among other things - glycogen, a storable form of glucose. The liver can only store about 100g of glucose (in the form of glycogen) then the rest gets sent into the bloodstream. Once the glucose hits our bloodstream our blood sugar level rises. This level must be brought down to a neutral level; otherwise our body will remain in a hyperglycemic state. Our body works to lower our blood-sugar levels by releasing insulin from the pancreas into our blood where it acts as a broom, sweeping everything from our bloodstream into our cells: proteins, fats, and glucose. The glucose will be swept either into our muscles for short term usage, or into our fat cells for long term storage. As our body adapts to the insulin level in our blood it essentially becomes resistant to it, meaning that we need more and more of it in order to bring our blood sugar level back down. This creates a state of Insulin Resistance where insulin is in near constant production, signalling our body to stop burning fat and store it instead. On the flip side, if our blood sugar remains fairly steady with not a lot of spikes, we remain sensitive to insulin, ie. Insulin Sensitive. In order to keep insulin production low we must do all we can to ensure we are Insulin Sensitive vs Insulin Resistant:
Certain other foods and spices may have a small effect on your RMR:
This may seem like a lot of information; however, it is just the tip of the metabolism-iceberg! Often people will focus on the small and easy changes, – add cinnamon to their coffee, or eat more tuna – however the bigger the change, the bigger the results! Focussing on the big picture - exercise, food choices and sleep - can quite literally change your life. *All nutritional and fitness info must be discussed with your doctor before any changes to diet or exercise regime are implemented. Change nothing and nothing will change; without change, there can be no progress! Related articles: Insulin: Friend or Foe? Nutrition 101: Master the Basics The Ketogenic Diet: The Concept, Benefits, and Drawbacks  Comments are closed.
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