Exercising while fasted burns fat
You’ll notice that the amount of calories being burned are roughly the same (about 2000 Kcals), however during fasting a lot more of these calories are coming from fat. And, since the subjects were not eating any fat while fasting, this fat must have been body fat.
Remarkably good at regularting blood sugar
In clinical research there generally isn’t a concern that exercising while fasting will cause an ill effects to a persons blood sugar. The body is remarkably good at regulating blood sugar levels, even in the face of intense exercise.
One IF experiment
What’s going on here? I don’t know for sure. But going back to insulin again, there’s a good chance levels of this hormone are lower than before. Insulin encourages fat storage. Put another way, lower insulin means for efficient release of fat, which can be used to fuel the body. The reason that I’m not hungry is possibly because the body is ‘feeding’ off my fat. That might also explain how I’ve lost about 5 lbs and an inch has gone from my waist.
Leptin and Ghrelin
Leptin levels seem to go down significantly after 12 h of fasting, leading to increased body fat catabolism and leptin sensitivity. This is a good thing, since leptin resistance seems to frequently precede insulin resistance.
Insulin *resistance*? …no, the opposite!
Over time, however, you will very likely become more insulin sensitive. What is happening is compensatory adaptation, with different short-term and long-term responses. In the short term, your body is trying to become a more efficient fat-burning machine, and GH is involved in this adaptation. But in the short term, GH leads to insulin resistance, probably via actions on muscle and fat cells. This gradually improves in the long term, possibly through a concomitant increase in liver insulin sensitivity and glycogen storage capacity.
Muscle loss during short-term fasting
Can the benefits of intermittent fasting be achieved without muscle loss? The answer is “yes”, to the best of my knowledge.
Intermittent fasting, cortisol and blood sugar
So, while I agree that IF is part of our heritage, and that it can be helpful in certain situations, I don’t believe it’s an appropriate strategy for everyone.
Why? Because fasting can elevate cortisol levels. One of cortisol’s effects is that it raises blood sugar. So, in someone with blood sugar regulation issues, fasting can actually make them worse.
Intermittent Fasting: A Beginner’s Guide
But the track record of certain Intermittent Fasting protocols, both in scientific publications and in real-world practice, seems pretty impressive too. That’s why I decided to put some of these protocols to the test. I wanted to answer the following questions: “Is IF just another fad diet? Or is it something health and body conscious people should consider?”