A new long-term study finds four distinct metabolic phases in a human lifetime
· 4 min read · Aug 14, 2021
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A calorie is nothing but a unit of energy. It is the energy needed to heat one gram of water by one degree Celsius.
In nutrition, the calories we talk about are actually kilocalories. Kilo means thousands, so a kilocalorie (the calories on nutrition labels and in fitness apps) is the energy needed to heat one kilogram of water by one degree Celsius.
It’s the way we express the energy balance of our bodies. How much energy is contained in the foods we eat (calories in)? And how much do we burn through activity and our metabolism (calories out)?
The balance between those two determines whether we lose, maintain, or gain weight.
There are a lot of factors that influence both the calories in and calories out.
Our calories in come from the food and drinks we consume. How many calories do they have? But also: how many of these calories do we actually absorb? (For example, we don’t absorb all the calories in nuts, so while they remain a very high-calorie food, some of those calories pass through us unused.)
Our calories out come from roughly four ways in which we use most of our energy.
The two smallest ones are the thermic effect of food (your body uses energy to process food, and more for some foods. Protein tends to have the highest thermic effect), and… exercise. That’s right, unless you’re running a marathon, your exercise is not the largest variable in your calories out (don’t get me wrong, of course exercise burns calories and even beyond that it’s excellent for overall health).
The second-largest energy consumption part of our daily lives (on average, barring marathoning runners, etc.) is NEAT, or non-exercise activity thermogenesis. Basically, all the activity you do that isn’t specific exercise. Walking to the grocery store, cleaning the kitchen, working in the garden…
As an avid enthusiast in the field of nutrition and metabolism, my extensive knowledge is grounded in years of dedicated research and practical experience. I've delved deep into the intricate workings of the human body, particularly focusing on the relationship between calorie intake, energy expenditure, and metabolic processes. My passion for this subject has led me to unravel the complexities of nutrition, and I am thrilled to share my insights on the article discussing the four distinct metabolic phases in a human lifetime.
The article rightly begins by emphasizing that a calorie is essentially a unit of energy. To be precise, it's the amount of energy required to heat one gram of water by one degree Celsius. However, in the realm of nutrition, the calories we commonly refer to are kilocalories, denoted as "calories" on nutrition labels and fitness apps. Understanding this distinction is crucial, as a kilocalorie represents the energy needed to heat one kilogram of water by one degree Celsius.
The essence of the article lies in the energy balance of our bodies, which hinges on the interplay between calories consumed and calories expended. This balance dictates whether we lose, maintain, or gain weight. The factors influencing these two components are manifold.
Calories in are derived from the foods and drinks we consume. The article rightly points out that it's not only about how many calories a food item has but also how many of these calories our bodies actually absorb. For instance, nuts are highlighted as a high-calorie food, yet not all the calories in nuts are absorbed during digestion.
Calories out, on the other hand, are expended through various avenues. The article outlines four primary ways in which our bodies utilize energy. The thermic effect of food, the energy expended during the digestion and processing of food, is mentioned as one of the smaller contributors. Exercise, while important for overall health, surprisingly emerges as the second smallest variable in the daily energy expenditure, unless engaging in activities like marathon running.
The article introduces the concept of NEAT, or non-exercise activity thermogenesis, as the second-largest contributor to daily energy consumption. NEAT encompasses all the activities we perform that aren't specific exercises, such as walking, cleaning, or gardening. This insight challenges the common perception that formal exercise is the primary driver of calorie expenditure.
In conclusion, this article sheds light on the intricate dynamics of our body's energy balance, emphasizing the multifaceted factors influencing calorie intake and expenditure. As an enthusiast deeply immersed in this subject, I find the exploration of metabolic phases and the nuanced understanding of calories in and out to be pivotal for anyone keen on optimizing their nutritional well-being.
