dear client first of all i would want to know what is his weight and height..and is he under weight since begining or has he lost it over a priod of time in case if its too low ..then we should look into the following causes of low weight here they are 1} genetic 2}increased metabolic rate 3)lack of proper nutrition 4)thyroid disorders 5)malabsorption aur commonly called as indigestion other rare medical causes are 1) chronic illness like tuberculosis if his weight loss is associated with following symptoms then he needs a checkup fatigue and early tiredness irritablity weakness anemia getting frequent infections increased sweating increased frequency of defecation rapid weight loss considering it to be a normal genetic built ..here are the following measures to restore weight 1) a balanced diet including proteins ans carbs..like eggs,,fish..pulses..milk.. 2)nuts like walnut almonds figs daily 3} regular exercise to help utilize the nutrient effeciently 4)plenty glasses of water every day..around ten 5)AND MOST IMPORTANTLY A POSITIVE ATTITUDE AND PATIENCE YOU MUST KNOW PEOPLE SUFFERING FROM OVER WEIGHT AND OBESITY SPEND THOUSANDS OF RUPEES TO GET A LEAN PHYSIQUE..THERE WILL BE LOT MANY WHO WOULD ENVY YOUR HUSBAND :) ITS GOOD TO BE A LITTLE UNDER WEIGHT RATHER BEING OVER WEIGHT GOD BLESS