TFM often seems to endorse a low carbohydrate diet for weight loss
There is a minimum amount of carbohydrate needed for brain function. Go below that and your body starts destroying it's own protein to produce carbohydrate.
Any exercise above a certain intensity for a certain amount of time or longer requires carbohydrate fuel and in the absence of carbohydrate in your diet results in your body destroying it's own protein to produce carbohydrate or inability to exercise at that intensity
@shortstories That is not true. The brain can comfortably consume ketone bodies after an adjustment period. In the meantime, excess amino acids can be converted to glucose. If you train regularly you should be able to consume the carbs without depositing them.
You can lose muscle and still gain strength because you lost weight and because of nerve firing adaptations
I should have talked about a no carbohydrate diet.
I would estimate if you eat 700 Carbohydrate Calories that is enough if you are sedentary to reduce protein breakdown
If you exercise you need a little more carbohydrate to prevent protein breakdown
If you go under a certain amount you will break down more protein but can still gain strength due to weight loss and nerves
For exercise above a certain intensity for longer than a certain duration the body normally uses a process called Anaerobic Glycolysis to produce energy by turning carbohydrates into lactic acid
On a no carbohydrate diet once carbohydrate stores are depleted
Only carbs created from protein breakdown can be used for anaerobic glycolysis
Preventing long term high intensity exercise from being possible in the relative almost complete lack of carbs to convert to lactate