37 year old - just diagnosed

Just to reiterate @primek’s point, your chemo dose is calculated on your weight and height. If your weight alters during treatment, your dose will be adjusted accordingly. I don’t have any stats but it certainly appears that more people put weight on during chemo than lose it (I did lose weight and could afford to do so).  As everyone says, the first few weeks can be very stressful but things often improve when you and your medical team have agreed on a course of action and you actually start treatment. Best wishes.