Part one of this two-part Seminal Review covers the fundamentals of energy balance to clarify how our body weight is regulated and the factors that can impact body weight changes.
Roughly five years ago, top metabolism and body weight researchers released a meta-analysis indicating similar effectiveness of low fat vs. low carb diets. A year ago, another group of researchers decided to perform another meta-analysis, including different studies that seemed to change the narrative of calories vs. carbs. In this 2-part Seminal Review, we’re going to break down the basics so you can have a better understanding as we go into a research debate.
What’s the Problem?
Many people struggle with excess body weight and weight loss challenges, apparent from the global obesity health problem. The most accepted explanation for changes in body weight is energy balance or the number of calories consumed vs. expended, aka calories in vs. calories out. While this common saying may seem like we’re beating a dead horse, it’s also overly simplifying a frustrating and complicated process…dieting. If weight loss were easy, obesity wouldn't still be a global health issue. Why is weight loss so difficult for some people? Why do people tend to gain weight during adulthood? The increased availability of calorie-dense foods has played a role in the drastic increases in body weight over the last several decades. It’s likely a combination of contributing factors, but we need to identify tools to prevent weight gain or improve weight loss to combat increasing body fat levels. If people could understand the simple concept of energy balance, that should equip them with the tools they need to eat less and move more, right? Are obese and overweight people just lacking willpower and discipline?
Perhaps there's more to the energy balance story than has been portrayed. While energy balance is scientifically sound and straightforward, many people often need to pay more attention to the multifaceted and complex underlying factors that influence energy balance components. Because of the complexities in understanding the science behind metabolism and changes in body weight, fad diets and other gimmicky health food products have taken advantage of unaware consumers. Adding to the difficulties, wild claims from celebrities, influencers, doctors, and scientists have portrayed diet culture and fads as appealing weight loss methods. In reality, diet fads and “diet tactics” leave people more frustrated and disheartened after wasting time and money, leaving them in the same place, if not worse.
This two-part Seminal Review will cover the fundamentals of metabolism, energy balance, and other factors impacting weight change. In the first part here, we’re going to focus on the underlying fundamentals of energy balance, how we measure it and what it can tell us about weight change.
Metabolism is a broad term encompassing a variety of definitions and meanings. While the physical digestion of food occurs throughout the digestive system in the stomach, intestines, etc. Your metabolism is an energy transfer system. You can think of it as the engine that converts energy within the foods we eat into the energy currency our bodies need to perform essential life functions and exercise. Specifically, the stored energy within the bounds of nutrients is converted into the usable energy of the body’s cells (ATP). This occurs through a series of metabolic pathways within the body’s cells, resulting in chemical byproducts of carbon dioxide, water, and heat. In research, the idea is to control energy intake and energy expenditure. This is energy balance, which we’ll cover later, but we want to focus here on how we measure “metabolism.” Metabolism is measured through estimating energy expenditure.