Hello and welcome to HCM.
As a specialist,i can fully understand your concern.
At 65 years age,most people face mid-life crisis, leading to
stress.
Majority respond very well to Fluoxetine(
Prozac). It doesn't affect energy levels, neither cause weight changes.
During stress, many people are prone to eat more or avoid eating normally.
This's the main reason for body weight changes, over a period of time.
So, be happy that you're advised an effective and safe medication.The exact period of response to this medication,is difficult to predict, but usually, it's about 2-3 weeks.If you've any doubt,send it to me,as a direct question.
Dr.Matthew J. Mangat.