Metabolic Misconceptions
by Fred Dimmenna

A little knowledge can be a dangerous thing! Case in point: Exercise "experts," who espouse regimens that will help you achieve all of your fitness-related objectives. In many cases, the facts being used to support these principles are legitimate ones, but ones that only represent a small piece of the puzzle. It is safe to say the topic that is most frequently abused in the aforementioned manner is metabolism and how it impacts exercise and dietary strategies. Metabolism is a word frequently bandied about in the media. It even finds its way into everyday conversation. It is not unusual, for example, to hear people refer to their metabolism as being slow, a fate worse than death for the average weight-conscious person. With the prevalence of obesity in the United States reaching epidemic proportions and the health ramifications of such, it’s not far-fetched to think that for many Americans, this appraisal is accurate.
But what does metabolism actually mean? Metabolism is the sum of all of the chemical reactions that take place in the living organism. Our bodies function like perpetual power plants, continually transferring energy between substances in order to perform work. This constant chore is necessary because there are myriad energy-dependent processes associated with simply continuing to exist. In fact, even when we are fast asleep, many energy needs are present. But as you might remember from high school chemistry class, energy can neither be created nor destroyed, so our survival depends on taking it in.
Metabolic reactions in the body come in two forms those that build things up from smaller sub-units (anabolic reactions) and others that break substances down (catabolic reactions). Catabolic reactions generate energy whereas anabolic ones require it. As a result, the two processes are coupled such that any energy-requiring (endergonic) reaction cannot occur by itself; it must be driven by a simultaneous energy-releasing (exergonic) one. It is like a boulder perched atop a hill: Much energy will be released (kinetic energy or energy of motion) when the boulder rolls down, but it took a significant expenditure to place it in its ready-to-deliver position in the first place.
Like the perched boulder, food contains potential energy that can be harnessed to perform work. The endergonic process of photosynthesis is responsible for establishing these energy stores, which exist in the form of carbohydrates, fats and proteins (the macronutrients). Photosynthesis is powered by sunlight, which is absorbed by the leaves of plants. Plants use this energy to synthesize the aforementioned macronutrients from carbon dioxide and water, giving off oxygen in the process. We require oxygen to exist, eat the plant (or an animal that has eaten the plant) to tap its energy and give off carbon dioxide when we break down what we ingest to reap the energy it contains. It is a remarkable system in which each component sustains the other.
Once we ingest potential energy, we have to turn it into a form that we can readily use to power the many endergonic reactions associated with life. These include those designed solely to maintain our existence (which cumulatively make up energy demands known as the basal metabolic rate), as well as any energy we need above baseline to accomplish all of the activities we undertake. Even processing the foods we eat requires energy to break down large substances and release the macronutrients, as well as to store this fuel and prepare it for eventual utilization.

The currency the body uses to transfer energy is a compound called adenosine triphosphate (ATP). The potential energy contained within ATP is used to drive all of the body’s endergonic processes. The link between the ingested macronutrients and this energy-rich transfer mechanism is the critical aspect of metabolism around which many of the aforementioned misconceptions revolve. All work within the body requires ATP and we synthesize this important intermediary from the energy contained in the foods we eat. But much like many of the body’s processes, this conversion is not as simple as it sounds. In fact, if it merely functioned like your automobile engine (which needs oxygen, so that the fuel it ingests (gasoline) can be utilized, we would certainly exhaust our ATP stores any time we attempted a challenging activity (sprinting, lifting weights or even getting up to walk without allowing a sufficient opportunity for the system to gear up). It is imperative that ATP concentrations never diminish significantly, so a number of other mechanisms must be in place to help out when the going gets tough. Needless to say, these play a major role when we are exercising. In addition, this dramatically impacts which macronutrient the body will use to recycle ATP. Because fat use is a top priority on any weight-conscious exerciser’s list, it’s obvious that this has some important ramifications.

Fred DiMenna, a Certified Strength and Conditioning Specialist and Lifestyle and Weight Management Consultant is a two-time Natural Mr. United States and a WNBF drug-free professional bodybuilder. Visit him at or email: