Originally Posted by Eason
It will cause your thyroid levels, and testosterone to go hit bottom while your cortisol will go up. Your metabolism gets repressed, I call that damage. These are physiological facts.
It sounds to me like you are regurgitating the shit of fear-mongers, rather than sharing any useful science. Long-term fasting and/or calorie restriction affect baseline levels of these hormones. The effect, however, is not cumulative (i.e., testosterone levels don't continue to drop as the fast goes on, and cortisol levels don't continue to rise). These baselines return to normal as soon as the fast is broken and/or calorie intake is restored. The metabolism changes during a fast, yes. It also returns to normal after the fast. That's the science.
Now, whether or not this damaging is all about context. Certain people will definitely experience negative effects from these hormonal changes:
- people will blood sugar regulation issues
- people with existing thyroid issues
- people with already low testosterone levels
- people with already low body-fat levels
- people with little muscle mass
The horror stories that get told about "starvation diets" aren't about the diet. They are about anorexia. People with already low levels of body fat shouldn't undertake long-term fasts or calorie restriction. Bad things happen. Duh. They experience negative effects even after they go back to normal eating. Because of the caloric restriction? No. Because they are underweight and malnourished and this has negative effects on their health.
In my case, I'm a generally healthy 28 year-old with no thyroid issues, no blood sugar issues, healthy testosterone levels, significant muscle mass levels, and greater than 20 percent body-fat. Will the PSMF effect my hormone levels? Yes. I expect to lose a little bit of muscle mass and a lot of fat as a result. After my body-fat levels have decreased (but while they are still within a healthy range), I will resume maintenance eating, my hormone levels will return to normal, and everything will be fine.