Metabolic Misconceptions: Part 3
by Fred Dimenna, CSCS

The attendance of the energy-storage hormone insulin decreases lipolysis (the breakdown of fat stores within the body). Insulin has an inhibitory effect on enzymes responsible for fat mobilization, so it’s easy to see why people consider its release the root of all weight gain evil. Insulin release is activated when blood sugar is elevated through post carbohydrate ingestion. The end result is the belief that only low carbohydrate diets that cause a reduction in insulin will rid your body of fat.

The facts about insulin’s anti-lipolytic influence are true, but often taken out of context. The real determinant of whether you access and use the fat you have stored is how much energy you use throughout your day versus how much you take in. If you ingest less energy than you expend, you will lose body fat, no matter how much insulin you have floating around in your bloodstream.

Insulin release only accounts for half of the blood sugar control puzzle. How effective insulin is in facilitating cellular uptake is also a critical factor. If your insulin receptor sensitivity is very high, a small amount of circulating hormone will suffice. Good glucose control is a key capacity lacking in many overweight people. This begs the question: How can insulin receptor sensitivity be enhanced?

The jury is still out on this one. Certainly, excessive intake of sugars could cause a constant load that would "wear out" receptors. This would be the supply-side of the simple “supply and demand” interpretation of the problem, the one that is currently in vogue. A demand-related component, on the other hand, is often ignored, but may be equally or more important. Consider what happens when we make our bodies efficient fuel users.

Exercise has many effects on endocrine function. One is to increase insulin receptor sensitivity so that less of the hormone needs to be present to control blood sugar. Challenging physical activity also allows for glucose uptake in skeletal muscles and in the heart (tissues that normally require the presence of insulin to unlock their glucose storage "vaults"). This occurs during exercise and in the immediate post-exercise period and allows an easy-to-access fuel (glycogen) to be readily replenished so that these tissues are restocked when future needs arise. Challenging physical activity also results in chronic enzymatic changes that cause overall glycogen storage capacity to increase thereby preventing fat accumulation.

Okay, let’s get back to energy balance and how fat stores are actually reduced. Metabolism is a catch-all term that encompasses all of the chemical reactions that occur in your body. Some of these are present even if you are not active (collectively termed the basal energy requirement), while others are associated with all of the activities you do above and beyond baseline. Even digestion and assimilation of the energy you ingest in the foods you eat is an energy-requiring process that must be accounted for. As a result, when you sum up all of your energy needs, the total represents the amount you will have to ingest in order to maintain your current accumulation of body fat. Eat less and your body has no choice but to access existing stores.

Considering the realities of energy balance, it is obvious there are two ways to go about reducing existing fat stores: either ingest less energy or expend more. Both these strategies can be used effectively, but there are drawbacks associated with the former. Dramatically reduced or excessively low energy intake levels put the body in a defense mode where maintenance of what is currently available to satisfy the deficit (existing fat stores) is the top priority. This means save energy at all costs! Your metabolism takes a hit and, before you know it, you’re eating a lot less and not losing an ounce.

Increasing expenditure is a far better alternative. Challenging physical activity cannot be made more efficient no matter how well conditioned you become; the energy cost of an absolute work rate remains virtually unchanged. In addition, if your capacity to perform that work improves, your ability to sustain higher levels of expenditure for extended periods will be enhanced. This will allow you to regularly reduce those well-stocked glycogen stores, leaving your body no other option but to use fat, which it can do more effectively when you are well-conditioned.

As you can see, challenging physical activity is the key for losing stored fat. Consequently, instead of worrying so much about less insulin, weight-conscious individuals should be more focused on putting the insulin they do release to better use. But this requires more than a nonchalant approach at the health club. In fact, the prevalent belief that a comfortable exercise pace that maximizes fat use is appropriate is the next metabolic misconception I’ll tackle.

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: