Feel the pain of overweight cyclists

I'd thought I'd chime in, since I'm in the same seat, so to speak. Lots of good advice here! Here are some additions:
- Spinning in a low gear is all well and good. But you get faster by going faster. Try keeping it in the big ring as much as possible for a ride now and then and get up from the saddle in the hills. This builds morale, also strengthens your legs and hearth. (Don't bust your heart, though. Or your knees. You'd might want to be further along your weight loss scheme for this.)
- Bikebot already mentioned intervals. Intervals are good. (This reminds me, I should do intervals)
- As far as I know, when the liver is processing ethanol, it can't burn fat. This takes a while. Also, the energy content of alcohol is relatively high. Something to consider. (Keeping it occasional, myself.)

I've been back riding for about a year, and have lost 1 1/2 stone in that time (with a fair bit of yo-yo ing!) Big Mel is correct - at first you won't lose much weight because you're building muscle (but you should look and feel a bit better).

These are my thoughts on hills & weight loss:

Gearing - make sure your gears are low enough, and ride with a fast cadence.

Frequency - keep going and riding those hilly routes!

Diet - Replace some of your poorer choices with better quality foods (snacks was my weakness), rather than drastically changing your diet. Stopping my pre-bed cerial habit made a big difference too (it took a couple of weeks before I stopped feeling hungry before bed though).
Fuel your riding though - eat properly in advance of a ride, and if your ride is long enough, take food with you. It is important not to lose muscle strength as you lose weight!

Strava - can be a great way of tracking how much faster you are up specific hills - most hills have segments. On one hill I started off grovelling up it at 9 minutes plus, and I'm now down to a PB of 4:09. After a while you'll also notice a difference in how you feel (from struggling, to attacking it) and what gear you're using (started on 34x28, now I'm comfortable with 36x23 or higher). You don't have to be getting a PB every time, but it is a nice way of monitoring your improvement and keeping your motivation up.

Ditto with the seated approach. I'm never afraid to get in a low gear early and just spin my way up with a good cadence, I then tend to stand and attack the summit in a higher gear when I can see it. Better that than go in too fast and then quickly lose that momentum and find that even 34/30 isn't low enough.

I'm still just the wrong side of 100kg, but I really enjoy climbing. I'm never gonna win any KOMs, but then that's not why I go out riding

As a previous 100kg+ (Clydesdale category) rider, may I offer 2 points which reiterate the advice above.

1) You have the power - stay seated on the climbs, get in a low gear and spin your way to the top with a sustainable "time trial" level of effort.

2) Lose the weight - it's obvious and easier than building power. The objective is clearly defined and measurable. And the performance benefit will help you EVERYWHERE.

Don't lose the faith - as you build dense muscle you will not drop that much weight to begin with, but your body fat will go. Give yourself 3 seasons to get into shape.

'Sheer bloody mindedness and the ability to suffer.'

This, in addition to riding them a lot. I've always loved hills even though I'm a big lad, I made myself enjoy them and see the challenge in them. It's mostly mental, apart from the *pace* you go up them. Nothing beats a big lad pulling a train up a long hill and seeing skinny guys dropping off the group. You just have to remember that it's very unlikely to kill you so dig deep and drive on. I did the Cingles du Mont Ventoux at over 100kg, wasn't a problem in the slightest. People have gone much faster, sure - but I enjoyed it all and was never in any doubt that I'd do it.

Small change to diet and I'm back in the 80s ...hills just get better and better

When you are passed by someone climbing, take note of their cadence vs yours. If you're already in the granny gear, not much you can do, but a lot of people do instinctively use too high a gear or shift down late rather than maintain a light fast spin up a hill.

If you're on a longer ride, do take a few breaks out of the saddle and stretch the leg muscles.

If you're trying to lose weight and build up strength, you might want to look at how you can add some variation to your training. If you keep straining the same muscles in the same way, there's a diminishing return. Try something different, such as intervals (sprints) and see if your climbing is any better a few days later. In the past, I've seen my cycling improve after I resume running in the winter.

Bikes have a weird way of making you healthier. I've always enjoyed cooking so my diet has mostly been pretty good - freshly prepared food with lots of veg and not too much added salts and sugars. However before the bikes took over, I was a bit of a late night party machine. Huge binge alcohol intake, a lot of late night dancing and all sorts of naughty pills and powders too. Never made a conscious decision to give that all up, but when you really want to get up on a sunday morning to do 100km of hard graft, it suddenly makes a lot more sense to have a quiet night in on saturday, making sure the bike's running smoothly.
As I said, I've always been a good cook but now my meals are far more slanted to pre and post ride nutrition. Biggest problem there is involving my other half in portion size by accident. You forget that if someone isn't burning off the extra 10k calories a week, it's got to go somewhere....!

At 90kg and with a fondness for pies and ale, hills are never going to be my friend.

However I personally think it's a mental thing. You're not going to go so slowly that you fall off, and no matter how it feels, you're still going faster than walking. So just slot it in the bottom gear, put your hands on the tops (it opens your chest and lets more lovely oxygen in), and winch your way up.

Sheer bloody mindedness and the ability to suffer. Also convince yourself that something awful will happen in your life if you climb off. I often wear my Alp d'Huez top, which would mean untold amounts of shame if I baled out!

Just saw you've already lost a stone, that's great work. Have you altered your diet at all too?

Climb them more often? Ride in 34-32?
Strength to weight is what dictates hill climbing though, and it's a lot quicker to lose weight than it is to build enough muscle to push the guts and extra muscles uphill.