If you're obese, better talk to your doctor first before beginning some extreme weight loss exercise & eating less regime.
As for overweight people, I think lowering your weight a little at a time is the best way to keep it off. As for my case, I was looking for 'stick to the basics' course and found http://goo.gl/0bXTIl so you might want to give it a try.
Realistic weight loss is 1-2 pounds a week for sustainable and healthy weight loss. So, by 3 months, you could have lost anywhere from 12-25 pounds. To lose 1 pound per week, you need to cut out 500 calories in your diet or burn the equivalent through exercise per day (to total 3500 calories - equivalent to 1 lb of weight in 7 days)... to lose 2 pounds you need to cut out 1000 calories per day either by reducing your calorie consumption or increasing your exercise. You should try this online weight loss tool - it is based on your behaviors, nutrition awareness and your genes... it is free: http://www.gbhealthwatch.com/weight-control.php . The key is to be aware of the food calories you are taking in while also staying active (even just 1 half hour a day walking briskly!). One quick easy tip is cutting out all beverages with calories. In other words, stick to water only (and add lemon juice or try sparkling if you want a little variety!)- even diet beverages have their own set of potential risks associated with them and are better to avoid. Good luck!
About 2 lbs. a week. You want to lose weight HEALTHILY, though, otherwise you'll hurt your body and you won't keep it off. Just exercise every day for about an hour or so and eat a balanced diet of fruits and vegetables. I'd also recommend cutting out as much dairy and bread as possible. Breads and pastas are filled with carbs, and milk can be filled with unneeded calories, it's made for a baby cow to grow to be hundreds of pounds heavier than you are now, just think of it that way.
Everyone has a different metabolism. Some people are able to eat junk food and sweets and still not gain any weight. Take my friend for example: She eats burgers, poutine and ice cream. She smokes and drinks as well, but still looks amazing. You are simply unlucky because you were born with a low metabolism and attempting to lose weight would be, in my opinion, futile, and not only that; it would also be unfair because there are those that can stay thin, even when consuming food and drink with high calories and not exercising, and then there are, well, others who would have to work hard in order to lose weight.
Ten pounds a month is what we tell our patients. When you lose weight slower, you have a greater success rate of keeping the weight off for good. By cutting portions in half, you can manage your weight for life, and remember, walk, walk, walk.