It is not unusual when discussions about weight management start to hear the conversation steer towards energy balance. After all when put quite simply it’s just “Energy-in Vs. Energy-out” what could be simpler? Well as it turns out a lot of things are simpler and that is because although this equation is fundamentally sound there are a lot of things that are going to impact on this.
Energy balance - Energy in
Numerous factors affect energy in and in its simplest manifestation it is just a case of count how many kcal we eat, job done. But now you have to start looking at other factors. For instance:
- How often are you eating? We know meal frequency impacts on the energy in equation.
- What is the composition of each meal? The fat content will slow emptying from the stomach and this may indirectly affect how many kcal are absorbed. The fibre content of the meal will also influence absorption rate and how much is absorbed. Finally the thermic effect of each macronutrient (Fat, Carbohydrate, and Fat) is different. This means that a diet very high in protein will burn extra kcal as part of the digestive process. Equally a very high fat diet will burn far less kcal’s as part of this process.
- Evidence is coming to light that your gut flora impacts on the energy derived from certain nutrients. This is important because what this implies is that two individuals eating the exact same meals may absorb a different number of kcal.
Clearly from this short and by no means comprehensive list you can see that energy-in is not as straightforward as ‘how many kcal on the plate’. You have to look at the individual and consider all of the above. Obviously this is not easy to do as the majority of these factors are very difficult to measure. It therefore becomes a case of a degree of trial and error to find out what will work.
Energy balance - Energy out
Turning to energy out you would maybe assume that this is just a case of considering how much energy you burn. Well that is accurate, but in itself this is inherently difficult to measure. There is not time within the context of this article to discuss all the errors and difficulties associated with measuring energy expenditure. Suffice to say it is complex and difficult to do. Next what makes up the energy you burn is not down to exercise/activity alone. The first factor you have to consider is the basal metabolic rate (BMR). BMR is the amount of kcal you burn just to stay alive. A number of things impact this and again it is complex. First there is how much muscle you are carrying. Muscle is very metabolically active so burns a lot of kcal, even at rest. Next there is how much fat you are carrying and although nowhere near as active as muscle your fat plus your muscle pretty much makes up your overall weight. There are other elements that make up your weight but for the sake of argument I will stick with these two. Basically the heavier you are the more kcal’s you burn. The exact number could be calculated if you knew the proportion of muscle to fat as they both have a different metabolic component as I have already stated. Your environment will also dictate how many kcal you use; especially extremes of temperature. So when it is very cold you shiver to keep warm, this takes energy and when it is very hot you sweat in order to try an evaporate water to dissipate heat, again this takes energy. I’ve already stated that exercise/activity burns kcal as we all know, but again there are lots of things to consider.
- How much exercise
- What type of exercise
- How intense is the exercise
- What environmental conditions is the exercise performed under
- How fit are you
- How much do you weigh
Again not comprehensive but gives you an idea that it is not a straightforward factor. Finally you need to consider your ‘non exercise activity thermogenesis’ (NEAT). This takes into account twitching, fidgeting and general subtle movements that we all do, some more than others.
You could write a chapter in a book about ‘energy-in’ or ‘energy-out’ in fact books have been written about each exclusively as well as energy balance as a whole concept. This short article is just intended to highlight that it is not as straightforward as energy in versus energy out. The fundamental principle holds true for all weight management; if you eat more than you burn off you will get fatter – FACT. What is more difficult to do is to assess both sides of the equation and ascertain whether this has actually happened.
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