Will Fasting Hurt Metabolism?

Intermittent fasting will not harm your metabolism, assuming you'll be eating enough on you non-fasting days.

I found that article very unhelpful, because all the studies he cites about muscle loss -- all of them -- are studies done on healthy men. Overweight people's bodies do not react the same way to food withdrawal as slim people's bodies. And when you're talking about slight muscle loss for huge fat loss, well, think of it this way: muscles can be *easily* regained, simply by eating lots of protein and exercising. They're not gone forever! But most muscle loss is way overstated in weight loss because of the population being studied -- they don't *have* fat to burn instead, so of course they're going to burn muscle! But we, we have fat. It makes very little sense for a body attuned to seasonal loss/gain during feast/famine to immediately attack the muscles! We're built to store, and burn, fat first.

Then there's the studies on men extrapolated to women... All the hormone disregulation etc doesn't happen in fat women because our fat cells store estrogen, and *release it* as we lose weight. So our hormone levels don't fluctuate the same way a slim woman's would, etc.

I've had a hard time finding studies that have been done on obese people doing various diets, ironically doctors want "only slightly overweight" people because they want people who are as close to a "control" baseline as possible. When they use overweight people, they tend to use equal BMI in men and women, despite the fact that women have a way higher slim-weight BMI than men, and on and on.

So, read all these studies with a skeptical eye for how they're designed.

Healthy or over-weight... Fasting isn't 'nice' to your body... to say the least; mentally not nice, either.

Will it hurt your metabolism? Kind of tricky question, but I would say this... (in my non-expertise opinion) Fasting for longer than a week will probably drop your metabolism. If you were a healthy individual before the fast though, I wouldn't think that the metabolic drop would last for much longer than the period of fasting itself.

So... in my mind... if you fasted for longer than a week, and then came back to your normal eating habits - yes, you will experience a drop in metabolism. After another week (theoretical assumption) of your regular lifestyle, it should be back to normal. Of course... if you want to ramp it back up quicker, just pick of a more high-energy workout routine and eat a lot of 'healthy' calories (veggies, chicken, non-fastfood stuff, etc.)