Protein is considered the number one macronutrient for fat loss.
Protein keeps people feeling fuller longer,
It isn't readily used for energy nor stored as fat.
It facilitates the building and repair of muscle tissue, which in turn, burns more calories.
However, as with ANY food you can have too much of a good thing.
How Much Protein?
The human body has a limit to the amount of protein it can actually utilize daily. One of the most well respected research studies conducted by Dr. Peter Lemon determined that even athletes benefited from just .73 grams of protein per pound of body weight daily. src.
A more general rule of thumb suggests that people aim for 0.8g per pound of body weight (as per meta-analysis of protein requirements). Excess protein isn't harmful for those with proper functioning kidneys, but the notion that dieters benefit from massive quantities of protein is a myth perpetuated by the supplement industry.
Most people can shoot for around 20-30 grams of protein per meal. If this is something you wish to manage, use the macronutrient calculator.
Tipton, K. D., & Witard, O. C. (2007). Protein requirements and recommendations for athletes: relevance of ivory tower arguments for practical recommendations. Clinics in sports medicine, 26(1), 17-36. Link
Esmarck, B., Andersen, J. L., Olsen, S., Richter, E. A., Mizuno, M., & Kjær, M. (2001). Timing of postexercise protein intake is important for muscle hypertrophy with resistance training in elderly humans. The Journal of physiology, 535(1), 301-311.Link
Rand, W. M., Pellett, P. L., & Young, V. R. (2003). Meta-analysis of nitrogen balance studies for estimating protein requirements in healthy adults. The American journal of clinical nutrition, 77(1), 109-127. Link