Note this is not an article on why you should train BJJ instead of other martial arts, although it will inevitably compare them on some level.
Its very intensive training, warm ups are going to vary from club to club but sparring is hard no matter where you go. Ive never heard of anyone not getting fitter through BJJ, weight loss is practically guaranteed just through sheer sweat. Whilst BJJ does not rely on strength, your grip and upper body strength will be put through its paces. Check this article and podcast on BJJ related fitness and weight loss: Fightworks Podcast
As a ground grappling art it is very low impact compared to a striking or throwing art (although BJJ does include throws). Even when sparring at 100% you can give up anytime and so injury is very often due to your own ego rather than your partners fault. Tapping is a very important part of BJJ, learning to do it well will go along way in keeping yourself injury free.
If you want to get fit, lose weight, gain flexability train in BJJ
BJJ has a very social and open atmosphere, there is alot of hand shaking, respect knuckles, "hang loose" pinky thumb handsigns and happy conversations. Its very laid back and relaxed. Bow, dont bow, whatever. It is a sport where you are very frequently giving people the oppertunity to break your limbs or put you to sleep, thus it is good policy to keep everyone happy!.
It is also a very competitive atmosphere, you are paying in cash, time, sweat and blood to get better at grappling. You want to beat your opponents. You want to win the competition. Along with the happy atmosphere I see this as a great strength, everyone is constantly helping each other and trying to push you to improve.
You are also promoted based on performance. If you can regularly beat the blue belts, pow! your a blue belt. So this means all the white belts are always gunning to beat the blue belts, the blue belts dont want to seem weak so they have to keep trying to improve to beat the experienced up and coming white belts. And they are gunning to try and beat the purple belts!. So their is a constant element on improving ones game, which is the whole point of training!.
BJJ does not believe in not stepping up to a challenge, it was made famous through a baptism of fire taking on any challengers from any art (see the early UFC's and challenge videos available on youtube). It didnt always win, but it always improved from it. It is not an ancient art, it is modern and is always trying to improve itself. If a technique does not work, it is not used. Bad techniques will not survive the process of validation. BJJ relies on leverage and simple body mechanics.
Ill avoid using cliche statistics, but Im sure most of you would of noticed a great deal of fights at some point going to the ground. From there BJJ can neutralise the size and strength of an opponent using little of your own. BJJ can also allow you to stay on your feet when in a multiple attacker scenario, where going to ground is not a great idea. Unless you live on a drug haven AIDS infested volcano, then BJJ is one of the most practical martial arts their is.
BJJ tests itself through competition, which is a great process of learning and pressure testing yourself. The rules will vary but will typically highlight positional dominance, always winning automatically via submission. The sport is growing very fast and is practised world wide, if you enjoy a sporting and competitive art then BJJ ticks all the boxes.
From its inception, BJJ has been linked with MMA organisations such as the UFC (mainly due to its effectiveness). Many MMA athletes will crosstrain in BJJ as their grappling art of choice, its impact on the sport is undeniable.
It is rare that I come across a BJJ student that hasnt migrated from another art that they have become dissatisfied with or lost interest in. It is a cynical martial art, everything is pressure tested. All claims to skill will be tested. You cannot fake being good at Jiu jitsu. Their are no 20th Dan 10 year olds. It is a great art that I and many love, there is an ever present air of energy where you know you are learning something usefull. You will get fit, have fun, learn self defense, compete in a great sport and make good friends.