Cant loose those extra LBS no matter what I do!! :(

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I have posted on these forums earlier regarding Insanity, and I have decided it might not be the brightest idea since I dont really consume too much calories. I am very confused to which approach I need to take.

I am 5 foot 7 (67) inches and 178 lbs (80kg), and I am a 24 year old male, and I need to lose 15 odd lbs. I generally like to consume between 1800-2000 calories a day, and I love doing cardio, maybe not as intense as Insanity, but burning 250-350 calories per session is very good for me. I have no problem doing anything I JUST CAN NEVER FIGURE OUT HOW MUCH CALORIE INTAKE will help me loose those lbs.

I have read in so many different places who give different information, is there anyone with proven inch loss experience who could give me a hand, preferably a male whose weight/height/age might be slightly similar to mine? Of course advice welcome from anyone with good experience.

Thank you