Dr Saurabh Sethi, a gastroenterologist who has been trained at Harvard & AIIMS, listed 5 warning signs that suggest a person's body needs more nutrition. The signs include brittle nails, suggesting protein deficiency, and twitching in eyelids or limbs, suggesting that there's a magnesium deficiency. Clicking sounds in joints, premature greying and getting bruised easily were other signs he listed.