I'm 24 and I try to keep my heart rate above 155 on the bike... It usually peaks somewhere around 177 on my normal warmup.

Hop off the bike, hit the weights or machines, hop back on the bike, stretch, go home. :thumbup:

As for diet, if weight loss is your goal, try to avoid carbs except before workouts. No fast food or junk. Keep proportions smaller and don't eat after dinner. I recently started replacing meals with a small Jamba Juice, but I'm not trying to loose weight, just sorta be healthier.