Cycling and weightloss?

I am cycling at high mountain bike settings Monday-Friday for over an hour long.

On weekends I am cycling 1 1/2 hours.

Now for the muscles, will they be compact or bulky on the more restraint setting?

Also how much weight in one week do you suppose a person starting out can burn/loose.

Cycling at a higher cadence 70-90 rpm’s with lite pressure on the pedals will burn fat more then high pressure and a low cadence. The high cadence will allow your body to use your slow twitch muscles that use fat as fuel. Low rpm’s and high resistance is like weight lifting and will incorporate your fast twitch muscles that use glycogen as fuel and will cause your muscles to tire easier.

Calories burned depends on your weight, speed, wind speed and incline.

You will never get bulky muscles by cycling period.

You weight loss depends on calories expended and those eaten.
Weight loss is all about math. A pound of fat is equal to about 3500 calories. If you burn that much through exercise or cut that much from your diet, you should lose that much weight. Of course the details get a little more murky. Will you lose fat or muscle? How much are you really eating? How much are you really exercising? How many calories do you burn just sitting around? And on and on…

The short answer is it’s realistic to lose about 1 to 2 pounds per week. More than that and you’ll likely rebound later or get sick. Rapid loss in the first week or two of a diet is always due to water so don’t get fooled. It’s easy to lose 5-7 pounds when you suddenly change your diet and exercise habits.

If your exercise is limited to cycling or riding a trainer, your muscles will not likely get ‘bulky’. It takes months (if not years) to see a real change in musculature so I wouldn’t worry about it. If you’re really worried, look at someone who rides a bike professionally. They are all rail thin and lanky, not bulky.

Hope that helps.
I started riding more seriously in May of this year, at a weight of 219-222 lbs. I’m 5’11" and 37 years old. I made a commitment to ride at least 3x per week and get at least an hour of strenuous exercise out of it. Generally 10-12 miles, but depends on the terrain. I was more concerned with the total time spent pedaling. I ride a 35lb hardtail mountain bike with a low-end front shock.
Throughout the summer I have consistently lost about 1.5 to 2 lbs per week. I have not drastically changed my diet, except to completely cut out beer and wine. I’ve had maybe 2-3 drinks per month since April.
Today I’m weighing in at 191-194.
I think most trainers will tell you to give your muscles two days to recover between workouts.
My wife gave me the book:"How to get Wheely Fit" by Oliver Roberts. It is directed at road riding, but has some good information and tips.
The things which have helped me the most in weight loss and fitness are the elimination of alcohol, using a cycling computer to log times on the same route, week after week. I set a baseline, taking times at certain intersections or points on the trail. Then, next time on the same route, I would set an interval timer to improve the time. This was all done in response to the fat that I could not find a reliable biking partner, so I had to compete against my own times. One other thing that helped, I joined the local mountain biking club, which has regular rides, and members of all fitness levels. It was only $20 to join, but you can usually show up at rides for free. Riding with people above your skill and fitness level will surely kick your butt, but it will also make you better. Tell them what you are trying to do so they know and will help you.
I played mind games with myself. I asked myself "Am I really taking it as hard as I can?" I discovered that by paying attention to ‘the ragged edge’, it would get pushed further and further out. I could ride harder, longer. And that was when the exercise stopped and the fun began. Best of luck to you, sister of the road.
There are a lot of factors that come into play. One is the amount of effort you are putting out… I found some information on calorie expenditure per hour, and it lists "Bicycling, Mountain or BMX" as 540 calories for a 140 lb person, and 753 calories for a 190 lb person. So, body size and your fitness level matter, as well as how hard you are pushing yourself. A bigger person who is more out of shape will burn more calories compared to a smaller, very fit person.

Obviously, it also depends on how much and what you are eating. if you put in more than you burn off, then you can’t expect any weight loss. if the weight you lose is mostly from sweat, then the loss will be short-lived, and indicates you are not drinking enough water. for instance, on summer days i go road biking about 4 hrs at 18-20 mph. weighing myself before and after the ride, i usually lose about 3-5 lbs during the ride.. but i gain that back over the next day or so as i replenish my fluids. so overall i don’t really lose weight in the long run, but i’m pretty close to the ideal weight for my body type already.

my muscles have definitely compacted a lot since i’ve been riding regularly. especially in my arms and legs. they are very toned now. i don’t lift weights at all, as it would affect my climbing.

also, relating to your effort, a lot of people talk about the importance of your heart rate, and what you burn in certain heart rate zones. you can google search for ways to calculate your "target heart rate zone" (based on age and resting heart rate). if you do most of your riding inside of that target heart rate zone, it is said that you are burning more fat. at other times you will be burning sugar and/or muscle. obviously you’d need a decent heart rate monitor; Polar makes some decent ones around $90