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The relationship between calories consumed and calories used is called
Energy used relies on the size of our body, the types of food we eat, and
our activity level.
Losing weight require an energy deficit: eating less calories than we use.
Gaining weight requires an energy surplus: eating more calories than you use.
We have the greatest control over our physical activity with regards to energy use.
We have total control over the energy we consume.
In the three previous posts we have introduced the three macronutrients from which we get most of our energy (remember, alcohol can also be a source of energy - not optimal, but still a source). Of course, we also use, or burn, energy throughout the day. The relationship between how much energy we consume versus how much energy we use is called energy balance.
The accounting of energy consumed is fairly straightforward. There will be some variation between individuals due to difference in absorption and metabolism, but energy input tends to be more simple than energy output.
Energy output (the energy we use) is more complex, but the three most important factors are resting energy expenditure (REE), the thermic effect of food (TEF), and the energy expenditure of physical activity (EEPA).
REE is essentially how much energy one needs to keep their body functioning (excluding digestion) while resting in a comfortable environment. It accounts for about 55-75% of how much energy someone needs in a day. REE is largely based on body composition. Organs tend to account for 60% of REE and muscle accounts for about 25%. Fat mass usually only accounts for about 5% of the REE; therefore, while people with more muscle do burn more calories, even at rest, a gain of a few pounds of muscle does not noticeably increase the need for calories.
The thermic effect of food (TEF) is the increase of energy use that is required to digest, absorb, transport, metabolize and/or store the energy in the foods we consume. This is where a calorie is not necessarily a calorie. For example, a protein tends to increase metabolism by 20-30%, carbohydrate by 5-10%, and fat by only 0-5%. This means that by eating more protein than fat, one can increase their metabolism without increased activity.
This means that some of the foods that we eat actually cause us to burn more calories - no no other work on our part - than other foods.
TEF usually peaks about an hour after eating and is usually finished within four hours. This is one reason that some people suggest eating more frequent meals. TEF may be responsible for between 5-10% of energy output.
Energy expenditure of physical activity (EEPA) is the output that most individuals have the greatest control over. It is also the most variable: a truly sedentary person is going to have a very low EEPA while someone who has a very physical job and works out at high intensity or for long periods of time is going to have a much higher EEPA. In addition to exercise and work, there are other ways that we burn energy without even thinking about it: fidgeting, activities of daily living, etc.
Energy balance is important for anyone that has any sort of physique, aesthetic, or body composition goals. That is, for anyone who wants to lose fat, gain muscle, maintain their size, etc., maintaining the proper proportion of energy intake and energy expenditure is essential.
Losing weight requires eating at a negative energy balance; that is, consuming fewer calories than one burns. Gaining weight requires eating more calories than one burns.
Unfortunately, as anyone who has tried to lose or gain weight unsuccessfully can tell you, it is not always that easy. One reason is that the body tries to maintain homeostasis. That means that it tries to keep the status quo.
If we eat at too small a caloric deficit or surplus, the body will naturally adjust so that we see no change. For example, eating more may result in greater fidgeting. Likewise, the opposite is true: eating less sometimes results in less non-exercise activity thermogensis (NEAT).
Cutting calories too drastically for too long can result in a metabolism that slows down to hang on to fat stores.
To compound the issue, some fat is harder to lose than other fat. The general understanding is that a pound of fat is equal to 3,500 kcal. Reducing caloric intake to create a 3,500 kcal deficit should be enough to lose one pound of body fat, but unfortunately, that is not always the case.
Losing fat is more like calculus than simple arithmetic.
So, too, is gaining muscle. Counting calories may be effective, but it may just add another layer of tedium and confusion.
The important thing with either goal is tracking behavior and determining what changes to make in order to continue to see results.
In the next post we will introduce the micronutrients and talk about why they are important.