Why do you need to lose 40 pounds in such a short span?Are you over weight? You should find out what your Body Mass Index is and what it should be if you are pretty close to the zone there is no reason to try and drop this much weight so fast.
http://www.nhlbisupport.com/bmi/bminojs.htm
Is there a particular reason or are you just wishing to drop weight?
If you are just trying to drop 40 pounds in general then you dont need to do it that fast in this case start doing some exercise do some calisthenics and change your diet some guys will try and lift weights but that adds more weight(the muscle) if you don't do something else you wont lose the fat and you will only gain more weight you'll have muscle but you will also still have the fat.
I am a fairly fit person but I really dont lift much weight I do tons of push-ups,pull ups, chin ups and dips though I also do lots of running and calisthenics that really burns up fat you can jump rope or hit a speed bag or punching bag, jumping jacks thats the stuff that burns fat.
Also stay away from greasy foods(no damn fast food ****e) and junk sugary foods instead of some sugar crap eat an apple or some other fruit and drink juice or water instead of soda you will also feel better as well. If you do not change your physical habits as well as your diet your not going to get good results.Many people think of diet as something they do to lose weight when you should really think about a diet as what you normally eat a Great White Shark prefers to eat seals that is its diet this is what I mean you have to always have a good diet only eat greasy fast food stuff rarely not a few times a week.
You should ask a Doctor more about a good diet every person is a bit different to some extent what is best for them.Of course avoiding fast food and greasy high fat foods and overly sugary foods is a good idea for anyone.I used to hate PE when I was a kid but in the military I loved it and have been very active every since.
http://www.menshealth.com/ is pretty good place to get ideas from.
I agree with NeonSamuari I have a friend who is 100% vegetarian and was over weight for a few years after he "converted" from meat the reason was because he was not active.Personally I dont believe in the whole veggie thing there a things your body needs from meats as well you just have to eat meat in much lesser amounts and better types of meat.
@CCIP you are in the normal zone for your BMI so you need to just exercise more if you have some flab better start busting out the sit ups and crunches.Being in active kills you sooner or later my Grandmother is 87 years old a she walks 2 miles just about every day and does that old lady pool exercise stuff she is in very good shape.My step dad his sister more or less sat around the house when she retired and now at 77 she can hardly get around.Humans have not evolved to the generally lazy inactive life style that the modern world lets a 1st world person live our bodies need activity to stay healthy only 10,000 years ago(really until the late 19th century) we where much more active because our survival depended on it and our bodies still function the same way but most of us dont so people are unhealthy as a result.