I'm not going to encourage/discourage whether your friend do anything - he's an adult (at least I hope he is). What I can chime is that I did a cycle when I was consider fat - I am 5'8 and was 205lb. I've probably worked out about a year before that cycle.
I originally took 500-600mg of Test E and ran it for 3 month. What I can say is that it was a total fail. Did I get stronger? Heck yeah, any exo-additive will help tremendously. Did I get buffed out like lot of members here? Heck no. I actually got fatter as I wasn't ready for the Test. Like any newbie - I wanted to get big/buffed without thinking about anything. I just wanted something to help me get there fast. In hindsight, my failure had to do with my attitude more than anything. Instead of keeping a good diet and workout regiment, I've relied on the Test E to do what I didn't wanted to do. So in the end, I came away thinking what the heck was that all about.
Now After 4 years later - due to bit of man problem, I went on TRT. When I started TRT, I can't say I was leaner - perhaps bit more muscular since I never stop lifting. But after some period (I am only taking 125mg per week), my body started to get leaner/harder and I haven't really changed my diet, although I was eating much better than when I was doing my 1st cycle.
The change was so dramatic that I changed my workout time as some people were noticing that I was changing bit fast and I didn't wanted them to suspect anything (still an upstanding citizen).
So moral of the story is that yes it can help a chubby guy but you have to be ready mentally and read as much as you can - and keep it simple. I say that because its really tempting to up the dosage as your body change but this is where mentally being ready helps tremendously.
One other thing I want to caution - his tendon is not ready for more weight and its easy to get injured (I did on my 1st cycle). Thats why lifting for while is important - as power increase, your muscle might accommodate but not tendons.
This is just my experience, hope your buddy can understand what I wrote.