Totally depands on how many calories your consuming and how many your burning when you're not riding your bike.
First, studies have shown that you can burn off only about 1% of your body weight of fat in a week. The rest will come from muscle. Unless you weigh 200 pounds, two pounds a week is too high a goal for you.
Second, the calories burned while cycling depends on the speed you are riding at, your weight, and inclines. This site has some estimates you can use to get an idea of burn:
The sore bum should feel better after a week or two of riding. Muscles take time, it will probably be a couple of months before you see major changes, but cycling will certainly tone legs.
As a huge believer in biking to lose weight I want to let you know its great for it!. But the first few weeks, even months may be tough. As one person said your butt may be sore for awhile, it goes away, not fast enough , but it does. Make sure you get a bike that fits you somewhat, you can get mightly sore if you dont. Also I know alot of people will tell you to buy an $$$ bike. I say buy a cheap one to start, if you really get into biking, then buy a good bike. Walmart and other toy stores close out bikes this time of year, I bought a bike last year for $38 (last years model, was normaly $120). The cheap bikes are heavy and wont take alot of abuse, but I dont abuse it, and heavy? So what, i want to burn calories. Dont overdo it, when you start to ride, slowely build up, take the first 10-20 minutes to slowly build up to a good pace, going fast right away always seems to burn me out right away. Also build up distance, first few time i rode, 3 miles seemed like riding to the moon, now i do 10 miles almost every night at about 13-15MPH (on a heavy slow cheap Mountain bike).
As for how much you need to do, wow thats a hard question to answer, bike computers are also cheap , about $15 at walmart, they may nbot be real acurate, but they can be a guide. Mine says the 10mile trip at my speed is about 400 calories at my wieght.
anything longer then 4-6 miles i would recomend drinking some water, keeping hydrated will keep your muscles from burning.
Dont think you need to do it all the first few times you go riding, build up to longer and faster trips. if you make it really hard work to start, less chance you will stick to it.
It takes about 3500 calories burned in excess of what you take in to lose a pound. So to lose 2 pounds per week, you'd have to burn an excess of 7000 calories per week, which is a LOT!! Especially since it's quite possible to eat all of that back very quickly!
Depending on your weight, sex, and height, and speed, and intensity of your ride, you'll burn anywhere from 500 to 1500 calories in an hour. Use a website (or this one) to figure that out, or you could always go with the 24-hour fitness Bodybugg, which tells you exactly how many calories you burn in a day. Another great cycling tool is a GPS (spring for an expensive one, it'll pay off - I recommend Garmin) - you can program your weight and your GPS tells you your speed, distance travelled, and calories burned!
Anyway - any form of exercise is great - I'm partial to cycling because I can sustain the activity for much longer than say, a jog. However, I will say it won't tone your bum (or your abs) as much as running or lunges or other gym-type workouts. Try rotating in a "standard" workout once a week at first, and then twice a week as you get into better shape. You'll work on toning all over, not just in the thighs!
Don't get frustrated if you don't lose enough weight or tone up much in the first month. Continue to drink lots of water and add mileage and eventually the pounds will fall off... Unfortunately, due to what I like to call "survival mode," your body may refuse to lose weight for a few weeks while it learns that "yes, I can survive with fewer calories per day," and finally decides to drop the pounds.
“How much do i need to ride my bike to lose weight?”
Here is one mans experience, yours will likely differ, but none the less, I wish I read this before I started on my weight loosing journey with my bike in spring of this year (2009).
I started riding my bike in March with the sole purpose of losing weight. Currently it’s the end of November. So far I have lost about 18 pounds. I have not changed my diet all that much, however, I must point out that I did quit eating out at restaurants (fast food or otherwise).
So far the experience has been terrific! I feel much more energetic and I have seen a HUGE drop in inches. I swear none of the pants that I wore before I started on my weight loosing journey fit me any longer. They are all loose. Typically when I wear my pants, I feel as though I am wearing baggy clothes (kind of embarrassing at times since my underpants are showing), even though just a few months ago (before I started riding), I was wonder if I needed to go to a larger size. My belts are all at their last loop and I expect that I will have to buy some new, smaller ones soon or at least cut a new hole in my current belts.
How did I get to this point? Well I didn’t go on a diet. However, I made a few changes to my eating habits. 1. I started eating breakfast. 2. I (almost) stopped eating out. 3. I eat a lot more veggies.
When do I bike? I ride about 5-6 days a week for about an hour. During summer months, I rode on a paved/semi-paved trail, during fall I’ve been riding on my trainer that I bought from a local bike shop for about $360, all riding is between 5PM and 8PM. If you think that $360 is a lot of money, looks at it this way… I’ve been riding the trainer since early September so 3 month (60 day of riding @ 5 days per week) which means it costs me 360/60 = $6 per ride. Scale that out over a course of 9 moths…12 moths…24 month. For the calories I burn and how good I feel, it’s a killer investment.
What else? After every 1 hour long bike ride, I do about 3 sets of crunches (about 1 minute each) with 20 pushups in between the crunches. So 3 minutes of crunches, 60 pushups. I feel incredible. Energy levels are up, weight is down, and muscle is up (which means I am burning weight just by going about my day)!
One more thing, I’ve noticed that my t-shirts don’t fit me as well as they used to. They are all super loose around my belly. That’s probably because my belly is gone now and I have an (almost) a perfect six pack. So I guess I will have to go to Gap/Old Navy/Kohls/etc to get some new T-shirt that better hog my new tight stomach. Nice problem to have!!!