Key Question: What is energy balance and why does it matter?
Whether you want to lose a bit of weight for the summer or gain weight and muscle at the gym, you need to understand energy balance. This first article will give you an overview of the different components of energy balance and why it is important for your health.
Your body weight over time is primarily determined by energy balance: which is the energy you consume (energy intake) versus the energy that you expend or burn. If you think of a set of traditional balance scales with energy intake on one side and energy expenditure on the other side, you are on the right lines. If the scales tip towards energy intake (you eat more than you expend) over weeks and months you will gain weight, and the reverse will happen if the balance is tipped towards energy expenditure (you burn more than you eat). Even small differences (30-50 calories per day) can result in changes in body weight in the long run.
If we start with energy intake, this is the food and drinks that you consume. There are three main macronutrients in the diet, carbohydrates (~ 4 calories per gram) fats (~ 9 calories per gram) and proteins (4 calories per gram), but for some of us alcohol (~ 7 calories per gram) contributes to our total energy intake. For most people around 5 % of the energy that goes into our mouths is excreted, but the remainder is burnt for energy or stored in the body as either carbohydrate (mostly in the muscle or liver) or as fat (mostly in the fat tissue).
On the other side of the scales is energy expenditure, which consists of three components. The first is your resting metabolic rate, which is the energy you burn just to stay alive, for example, for basic functions of your cells and the maintenance of your body temperature. For most people this resting metabolic rate will be 60-65% of your total energy expenditure and differences between people are mostly due to difference in body masses and how much muscle you have. For example, a bigger person will have a higher resting metabolic rate, because there is a greater mass of cells and tissues burning energy. A second component is diet induced thermogenesis and this is the energy you need to invest to break down, store or burn food you have eaten. The energy required (as a percentage of energy consumed), to digest and absorb fats, carbohydrates, alcohol and protein is ~ 0-3 %, 5-10 %, 15-27 % and 20-30 %, respectively. This explains why you can feel hot after having big meals especially if they are high in protein (e.g. your summer BBQ!!). The final component is physical activity energy expenditure, which consists of exercise but also non-exercise activities such as walking to the shops, doing laundry or gardening. This is important because someone who does exercise but has a sedentary job could burn the same amount of calories with physical activity as someone who doesn’t exercise but has a more active job (e.g. a gardener).
The complexity is that the two sides of your energy balance scales are also interlinked. If you change your diet and energy intake, your energy expenditure might be altered and vice versa. For example, if you skip breakfast research suggests that you might be subconsciously less active in the morning (e.g. less fidgeting) compared to if you eat breakfast. This means that the energy deficit (the difference between energy intake and expenditure) created by conscious lifestyle changes such as dieting or doing exercise could be eroded and you may lose less weight than you expected.
The difficulties with losing weight with exercise or diet will be discussed further in some of our upcoming articles! We will also discuss how you can monitor and track your energy intake, your energy expenditure and your body weight to give you the tools to help you manage your weight.
The take home message: For long-term changes in body weight it comes back to the basics, energy intake compared to energy expenditure. Having a knowledge of these components is important if considering a lifestyle change to alter your body weight.
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