Legs feel hollow after exercise

Try swimming. Your legs will feel like rubber bands.

If you are used to eating a lot of carbohydrates and have just recently reduced your carbohydrate intake, your body is probably still ramping up the enzymes it needs to generate energy from proteins and from body fat and dietary fat.

You may be hungry because your body is looking for a carb fix--you might have low blood sugar. But these swings will even out as your body gets used to the new food compostions you are choosing. (add: you might also have used up your muscles local stores of glycogen, rather than an overall low blood sugar).

You are interpreting your legs as feeling "hollow". I interpret my legs when I don't exercise as feeling "gunked up". It may be that you view "gunked up" as normal (because you are used to it) where I view "hollow" as normal.

Try longer duration, lower intensity exercise. Web search/read about "target heart rate" to learn what intensity of exercise you need to most efficiently get the effects you want.

Just my two cents here....I spent months in therapy after a spinal injury. My therapist always encouraged me to explain how I was 'feeling' as in not good/bad here but as in ' the swell of my lower back wants to fold in on itself because my stomach is too strong'. At first talking like this made me feel stupid. But as I progressed, it turned out my gibberish often told my therapist exactly how I was doing.

...Have you loss muscle mass on your diet? Could that be why your legs feel hollow?

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FWi My legs feel twitchy when I haven't exercised, happy when I did something mild and expand-y when I lifted.