EUGENIZATION.

Matt points to a highly compelling study in the American Journal of Endocrinology.  I think the title says it all:

Insulin-resistant muscle is exercise resistant.

Consider the study’s findings for a minute: Eating poorly is a double whammy.  Not only are you impairing your body’s ability to mobilize fat for energy (instead causing it to store that fat away for later), but you’re also impairing your body’s ability to generate more muscle, which would help to counteract those effects.

A quick primer on the concepts behind the study:

Insulin’s primary function is to regulate blood sugar levels by pulling sugar out of the bloodstream and into the cells.  Over time, too much ingestion of sugar (and things that break down into sugar - dietary carbohydrates) causes excessive levels of insulin in the blood, leading to insulin resistance.

Mitochondria are known as “the powerhouses of the cell”.  They literally supply the energy (ATP) that the body uses in all cellular functions (muscular contractions included).  If you think of muscles as the engine of the body, mitochondria would be the fuel tanks.  As you become more fit, your body creates more mitochondria (after all, more horsepower requires more fuel). 

At least, that’s what supposed to happen.  According to the study findings, if you’re already insulin-resistant (and obese), the mechanisms that code for mitochondrial proliferation are blunted (read: your body doesn’t produce mitochondria as easily).  The end result?  You (the insulin-resistant) don’t build muscle as well and find it harder to improve your fitness levels.  Yes, it’s a cruel, cruel world.

Just more reason for you to minimize the amount of sugar, starch, and grain in your diet if you’re looking to get the best results from your exercise program.