<human>: I've been seeing this guy for ~6 months. We have this thing where we call all our dates "adventures". Over the weekend we had a small argument and as an apology he now wants to take me on an actual adventure date. So he found this place in the forest where you do loads of physical activities like ziplining, climbing up nets, and going across tiny wooden bridges at the top of the trees.

The problem is that while he's really fit, I'm overweight. I'm 5'9" and 102 kg/225 lbs. I've checked and should fit into the harnesses, but I'm concerned that I won't be able to keep up physically as it apparently goes on for 2-3 hours and I'm a casual gym goer at best.

When he asked me I said that I was terrified of heights (which is also true) and would probably end up crying a lot. His response was that he's afraid of heights too and thought that this could be a brilliant way of "conquering our fears together". I don't have any other excuses to make without just telling him I might be too fat. I also do really want to do it as I think it would be a great bonding experience if all goes well.

So my question is do I just say yes and give it a go, risking potential embarrassment in front of him if I'm not fit enough? If I don't, do I make up an excuse? Do I tell him the truth?

Can you succinctly summarize the text in 1-3 sentences?
<bot>: I'm fat and afraid the guy I'm dating will realise just how fat I am when we can't go on an activity date together. Please help.