Many people who were not sensitive to salt become so when they take certain prescription drugs

Many people who were not sensitive to salt become so when they take certain prescription drugs. - Yes. These are some of the pharmaceutical drugs that cause salt sensitivity and a host of associated health problems: amitriptyline and the other tricyclic antidepressants, also many prescribed steroid meds, including HRT and some birth control meds, also Epilim and other anticonvulsants, and some painkillers, and some anti-psychotic drugs. And you can read here about other groups of people who are or who can become vulnerable to salt in different ways.

If your medication causes sodium retention you will gain weight and may become obese

There are many medications that cause sodium retention/fluid retention/water retention/weight gain/obesity/edema/swelling. Here are some of them: steroids and HRT, most antidepressants, antipsychotics, anti-epileptics, anticonvulsants, and more.

If you have become overweight/obese because of drug-induced sodium retention, you need to reduce your salt intake in order to lose weight. If you do not reduce your salt intake you will continue to gain weight, regardless of how many or how few calories you eat.