I haven't lost massive amounts, but I have tried triathlon training on a small (100-200c per day) deficit. It becomes tough fast as the steady cardio training generally makes you more hungry. What worked for me was fuelling well in the morning, during and just after exercise and then have a light meal in the evening to ensure a deficit. It also becomes very important to eat "good" calories, with veggies, protein, carbs and healthy fats. It leaves no room for cake/chips/cookies and soda. The only indulgence was sugary sports drinks and haribo during any training that lasted more than one hour.

I think most road bikes can take up to 125 kilos, but you can check on the manufacturers page.

One thing that might work better is to do a 6-week strength building program on a deficit, focusing on growing muscles and losing weight, before you start a triathlon training block.

Awesome! I dont have the answers, however i am trying to do the same. But for me it was a looooooongterm goal.

Started at 116kg Last year I did mostly muscle training with a personal coach. In combination with intermittent fasting.

That made me lose 20kg (96kg)

After that I started doing extra cardio training (cycling and swimming).

Planning to do this for at least half a year - year to lose another 10kg before I even start thinking about running.