I recently discovered by using Sparkpeople that I have consistently not been getting enough protein in my diet to support my fitness and nutrition goals. Protein does support muscle growth and repair, but you're not going to "bulk up" on pumpkin seeds.
Building muscle by eating a healthy amount of lean protein and doing strength-training exercise is an excellent way to turn your body into a calorie-burning machine. Healthy, fit muscles (built with protein) help your body burn off fat and metabolize the calories you take in efficiently.
I am a huge fan of healthy, lean protein and strength-training 2 or 3 times per week.....not enough to "bulk up" (I'm not looking to enter any weight lifting competitions, haha!) but enough to ensure my muscles are toned and strong. Since paying conscious attention to this issue in my own life, I have noticed a significant difference in my arm and leg strength, the tone and shapliness of my muscles, and my ability to stay feeling "full" after meals (protein can help you feel satisfied for an extended period of time after eating). An added bonus for women: strong muscles and strength-training exercise can help with bone density, which can help prevent osteoporosis later in life. All that to say, find out what your protein range per day should be, and aim for that with good, lean sources of protein. Pumpkinseeds and nuts are great, but in moderation as their fat content (though mostly good fats!) is quite high in larger quantities. Other good sources of protein are low fat dairy products, eggs, peanut and other nut butters, lean meats, fish, beans, and soy products. Variety is the spice of life!