Metabolic Misconceptions: Part 2
by Fred Dimenna, CSCS

Many exercisers adhere to principles designed to minimize fat storage and maximize fat use and unknowingly short circuit their attempt to lose fat and keep it off in the process. To understand why, consider what causes fat to accumulate in the first place. The foods we ingest contain protein, carbohydrate and fat in various proportions. These macronutrients can also be considered relative to the energy they provide. On average, a gram of protein or carbohydrate contains four calories of energy, while a gram of fat houses nine. Fat accumulates on the body when energy intake exceeds expenditure. This is a simple concept that is often misconstrued. For example, carbohydrates won’t make you fat anymore than protein or fat will, assuming you eat the appropriate amount. Take in more than you need, on the other hand, and you’ll store the excess, no matter what the source. It is simply a matter of supply and demand.

The anti-carbohydrate sentiment currently in vogue considers the circumstances directly following carbohydrate ingestion without recognizing the big picture. When you eat foods that contain carbohydrates (either simple sugars or complex versions that have less of a negative connotation), your blood sugar (glucose) will rise at a rate determined by the ease of breakdown of the particular sugar. When blood glucose rises, a hormone (insulin) is released to bring it back down to its ideal range. If all goes according to plan, blood glucose will stay relatively constant regardless of how much sugar you ingest. It is an amazing control mechanism, one that also affects other hormones to keep your internal environment balanced.

Maintaining blood glucose can be a tricky proposition. Imagine what happens when you introduce a high sugar load rapidly into your bloodstream. Glucose will soar if insulin isn’t released in sufficient quantity. In addition, insulin won’t be effective if it doesn’t "unlock" specific processes that facilitate sugar removal. Needless to say, where the sugar is sent also becomes an issue.The body stores carbohydrates in the form of glycogen, a long-chain molecule composed of hundreds of glucose units joined end to end. Glycogen is an efficient energy-storage mechanism that is found in numerous sites, including skeletal muscle, the heart and the liver. Generally, the vast majority is deposited in skeletal muscle and this is apropos because muscle is a significant energy user.

Liver stores are also important because they are broken down to raise blood glucose when levels drop below normal (during prolonged fasting, for example). Ideally, all excess blood sugar would be packed away as glycogen to provide easy-to-access fuel that is always available should the need for energy arise. Unfortunately, this cannot be accomplished. Other homeostatic mechanisms control glycogen synthesis and when reserves are deemed adequately stocked, further storage in this manner is impossible. At this point, another storage depot must be found. Enter the fat cell.

Insulin’s goal is to reduce blood glucose, no matter what that entails. When glycogen stores are fully loaded, it facilitates energy storage in a much less transient form as the energy-dense triglyceride molecule. Triglycerides are deposited in fat cells and cashed back in when needed, although accessing them is much more involved than breaking down glycogen.The body forms triglycerides by attaching fatty acids to a glycerol backbone. Insulin facilitates this process. Glucose from the blood is converted to glycerol, so insulin satisfies the need for this precursor. And if fatty acids are also present (let’s say you ate a juicy steak with your insulin-inducing baked potato), you’ve got all you need to build your fat stores. To make matters worse, fatty acids don’t only come from dietary fat, they can also be synthesized from protein, carbohydrates and alcohol. Consequently, insulin’s reputation as the energy-storage hormone is rightfully associated with triglyceride formation.

If you’re not quite ready to label insulin public-enemy number one, listen to this! The aforementioned series of events that causes triglyceride formation (synthesis) requires energy (it is an endergonic process), as does breaking the fat deposits down to release the energy they contain (lipolysis). Obviously, mechanisms must be in place to prevent both processes from occurring simultaneously, since such "futile cycling" would needlessly waste ATP. Consequently, when insulin is doing its thing, hormones that operate in an antithetical fashion are effectively shut down. Specifically, hormone-sensitive lipase, which initiates the cleavage of fatty acids from glycerol and mobilizes them for potential use, is rendered powerless. So, insulin is guilty as charged, right? Well, not so fast. Next month, I’ll consider the big picture and offer insulin’s defense.

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: