Plateau... that's what my doctor called that period where it seems as if you're not losing weight. There's a couple of things you can try to fire up the furnace again. The body gets used to routines. I've heard it called "muscle memory". A good idea would be, instead of riding the bike for 30 minutes a day, try switching to an eliptical machine.
I don't know what your lifting routine looks like, but simple changes there will help too. For instance, if you do bench press with a straight bar, use dumb bells instead or vice versa. If you do leg presses on a machine, do dead lifts with light weight instead. If you do arm curls with a curl bar or dumb bells, use a straight bar, or better yet... use the cables on the rack system. (I try to do at least 2 different exercises for each body part.) Also remember, as you stated about building muscle. Muscle takes up less room that fat, it also helps you burn those calories more efficiently.
Drink plenty of water and be patient. Little adjustments are necessary. I switch up about every 4 weeks.
The Peak 8 routine it will quickly raise your heart rate 8 times for very short bursts, with a cooling down period in between. Ideally you’ll be sprinting or cycling full throttle for 30 seconds with a 90 second cool down in between each outburst.
This is the fastest way to lose fat and build muscle in the body. Peak 8 actually stimulates the growth hormone in the body. I encourage you to visit Dr Mercola’s site to learn more about Peak 8 fitness because I personally feel that it is one of the best ways to exercise, especially considering the speed at which you can lose fat and build muscle.
I highly recommend you read this article and watch the videos on the page. It will give you all the information you need to know about Peak 8 – Flood Your Body With This “Youth Hormone” In Just 20 Minutes
What you eat after Peak 8 training does matter
It’s recommended that you do not eat sugar or carbohydrate for 2 hours after the Peak 8 exercise because these foods can impact the release of the growth hormone in the body. The link is below
http://fitness.mercola.com/sites/fitness/archive/2010/11/13/phil-campbell-on-peak-8-exercises.aspx
Figure your heart rate by this formula
The Karvonen Formula is a mathematical formula that helps you determine your target heart rate zone. The formula involves using your maximum heart rate (MHR) minus your age to come up with a target heart rate range (which is a percentage of your MHR). Staying within this range will help you work most effectively during your cardio workouts.
an example of the Karvonen formula for a 23 year old person with a resting heart rate of 65 beats per minute (*to get your resting heart rate, take your pulse for one full minute when you first wake up in the morning or after you've resting for a while). This formula also includes an updated calculation of maximum heart rate (the previous formula was 220 - age, which has now been shown to be inaccurate):
206.9 - (0.67 x 23 (age)) = 191
191 - 65 (resting heart rate) = 126
126 * 65% (low end of heart rate zone) OR 85% (high end) = 82 OR 107
82 + 65 (resting heart rate) = 147
107 + 65 (rhr) = 172
The target heart rate zone for this person would be 147 to 172
First thing in the morning before you get out of bed have a clock with a second hand and check your resting heart rate then figure your rate by the
Karvonen Formula above.
You burn 30 percent more fat from doing cardio after a weights session as opposed to cardio on its own.