A major problem us Americans deal with when it pertains to weight loss (and weight management, since it falls for this subject matter) is the consistency that you're eating well-balanced meals. Over and Under-eating is very common, especially in the age of "trendy" diets. The factors of height, weight, and environmental conditions are to be considered when it pertains to eating with your goal(s) in mind.
As a certified fitness professional, my primary focus is instruct the client on exercise and movement principals. Nutrition-wise, I'll give a basic educational breakdown of macro nutrients and it's role in strength gains, weight loss and weight management. Unfortunately, my role in nutritional instruction is limited since it is recommended one speaks to a licenced dietitian or nutritionist for a detailed analysis.
Generally speaking, macro nutrient items (carbs, proteins, fats) is best utilized when sectioning off in handful portion-sizes when having meals (Ex: Hand full-sized chicken breast, brown rice, asparagus, etc). Balancing meals with a special focus on vegetables, fruits, whole grains and lean protein sources will ensure balanced doses of vitamins and minerals. Additionally, a multi-vitamin supplement is helpful. Once again, talk to your nutritionist or dietitian for recommendations when it pertains to multi-vitamins and other supplements.