The majority of individuals who methodically track their food intake are preoccupied with the precise macronutrient breakdown of their diet. The reality is, the majority of your results will be determined by your total energy intake and your total energy output. In short, the most important thing is to focus on calorie counting/control.
Studies show that overweight individuals who lessen their caloric intake to a level that is moderately below their total energy expenditure experience significant health benefits, both in appearance (e.g. reduced waist circumference) and internally.
Now, this is not suggesting that macronutrient manipulation isn't necessary or worthwhile since frankly, it is. However, if you're not eating enough you won't build muscle; just like you won't lose fat if you're not limiting calorie intake enough.
So if you're new to tracking food intake, first and foremost monitor your calorie intake. Once you are comfortable with that, move onto macronutrient tracking/manipulation.
The trickiest part of discussing nutrition is trying to provide generalizations since dietary needs vary on an individual basis. However, there are still some guidelines to follow and below you will find out how to apply those and create your optimal eating plan.
Protein is crucial
Research seems to suggest that as long as the protein sources you ingest contain the necessary leucine content (and other essential amino acids) then there is little difference in MPS between sources (e.g. milk, animal protein, egg protein, etc). Generally, 20+ grams of a leucine-rich protein source will provide a sufficient elevation in muscle protein synthesis for a solid 3-4 hours post ingestion. That being said, protein needs will vary for everyone based on their training regimen, age and body composition.
Fats are essential
Fatty acids have a variety of roles in sustaining cellular integrity/functions. Unsaturated fat sources, especially the omega-3 fatty acids docosahexaenoic acid and eicosapentaenoic acid are revered for their cardiometabolic health benefits. Also, saturated fatty acids are necessary for proper hormone production (mainly androgens). Contrarily, too much saturated fat intake is associated with insulin resistance and metabolic maladaptations, so don't go overboard. As a baseline, start with about 25% of your total fat intake coming from saturated fats and emphasize unsaturated fats for the rest.
Carbohydrates are anabolic augmenters
Gym-goers often seem to have a love-hate attitude toward carbohydrates due to their inherent insulinogenic property (save for fructose). Lest they forget that some amino acids are also insulinogenic, and more importantly, that insulin is a potent anabolic hormone. Therefore if you want to pack on some solid muscle tissue, it is quite conducive to manipulate insulin secretion in your favor. Numerous studies have verified that the muscle protein synthesis response to a nominal dose of amino acids can be enhanced by the presence of an increased insulin response. Moreover, carbohydrates refill liver and muscle glycogen stores. The protein-sparing effect of carbohydrates is crucial to muscle building since fewer amino acids will be utilized for energetic purposes when sufficient glycogen and/or glucose is available.
Maximize pre-workout nutrition
Intense training elicits a myriad of acute metabolic effects, such as up-regulation of glucose transport proteins and enhanced blood flow in muscle tissue. It is important to take advantage of these favorable metabolic adaptations via proper nutrient intake around the training time frame, generally by eating a generous amount of carbohydrates and protein. This isn't to say you shouldn't take in any fat at this time either, but just not a large amount as fat can slow digestion and blunt insulin secretion.
Meal timing & frequency
The highest priority on the hierarchy of dieting is meeting your calorie and macronutrient quotas at the end of the day, with the timing of those meals falling on the bottom. However, meal timing and frequency is still of relevance in the grand scheme of things, but the most important thing is to have a plan that allows you to consistently hit your calorie/macronutrient goals and perform at your best. If this means eating 6-7 smaller meals every few hours or 2-3 bigger meals a day spaced further apart throughout the day then so be it. That being said, avoid very extreme protocols; eating all of your calories in one meal per day or eating every hour around the clock are certainly not very pragmatic approaches to performance nutrition.
Stay hydrated
Don't skimp on fluid intake, especially around the training time-frame. If you're constantly thirsty or your urine is dark yellow, you are likely not drinking enough fluid. Try and carry a water bottle with you throughout the day and drink several ounces every hour.