Fat Loss: Part 1 - Burning Calories or Workout Intensity?
Fat Loss: Part 2 - The Metabolic Syndrome
What if you could flip a switch to set off a fat-burning chain reaction to obliterate thousands of fat cells (particularly that stubborn belly fat), while allowing no fat storage? What if, as a result, you’d reduce inflammation, bad LDL cholesterol and the amount of insulin circulating in the body?
It has long been assumed that one needed to exercise at a certain intensity that was not so high as to get out of the “fat burning zone”, and that if the intensity crossed a certain threshold that fat would no longer be the fuel used for exercise. Indeed, during low intensity exercise, fat is predominantly used for energy production. The reasoning was that a person just needed to burn off a certain amount of calories through steady state activity to lose bodyfat. However, the reality is that the average person weighing 150 pounds burns roughly 100 calories per mile (and not all of those calories come exclusively from fat) – whether a person walks or runs. Since there are approximately 3500 calories in a pound of fat, a person would have to go 35 miles to burn 1 pound of bodyfat, so the theory went.
The Amplification Cascade
In an amplification cascade, rather than one molecule acting to produce one metabolic effect as outlined in the low-intensity exercise example above, one enzyme instead activates another set of enzymes, possibly ten or a hundred in the next step. Each one of those hundred in turn activates another hundred, and so on down the line – an exponential domino effect or chain reaction. This amplification cascade is extremely effective in supplying huge amounts of energy to our working muscles during an emergency or a “fight-or-flight” situation. It can also be safely induced during controlled high-intensity exercise performed above the lactate threshold.
The reason high-intensity exercise is so important for making such a dramatic metabolic shift is that it triggers both glycogenolysis and an enzyme called hormone-sensitive lipase.
Glycogenolysis – the breakdown of glycogen for use as energy within skeletal muscle – restores insulin sensitivity on muscle cells, which are the greatest glycogen depot in the body. When the fast twitch muscle fibers are activated during these “fight-or-flight” situations, stress hormones such as growth hormone and epinephrine are secreted. As a result, the muscle cell empties itself of a significant amount of glycogen, which means insulin can now act on the cell surface and allow glucose to reenter the muscle. This increase in insulin sensitivity is crucial to your metabolic health and keeping insulin levels low.
Hormone Sensitive Lipase
The same process that activates glycogenolysis also activates hormone-sensitive lipase and the mobilization of fatty acids for energy utilization. This fat-burning chain reaction is similar to what happens in glycogen mobilization. Fatty acids are a very important source of energy for muscles. However, if insulin levels are high, even with a low-calorie diet, hormone-sensitive lipase will be inhibited, and mobilizing fat will become impossible. This may be why people who diet and take up walking or jogging often find it difficult to lose much bodyfat.
This amplification cascade cannot be triggered with low-intensity steady-state exercise. The fast-twitch muscle fibers, the largest glycogen depot in the body, must be activated. Only through above-the-lactate-threshold, high-intensity exercise can this chain-reaction be accomplished.
In summary, high-intensity exercise training induces greater fat loss, in particular, abdominal visceral fat loss, than low-intensity exercise training for several reasons:
- First, high-intensity exercise induces secretion of lipolytic hormones, including growth hormone and epinephrine, which facilitates greater post-exercise energy expenditure and fat oxidation.
- Second, under equivalent levels of energy expenditure, high-intensity exercise training favors a greater negative energy balance compared with low-intensity exercise training.
Now, you are probably asking “What exercises should I be doing?”, and “How often should I do them?” Another question, most importantly, is “How can I do this safely?”
We’ll be providing the answers in upcoming articles.