One of the most important things to be eating consistently for fat loss, muscle gain and to acquire a better body composition, is protein.
Protein will keep you feeling fuller for longer, help to build muscle tone and also increase your metabolism.
Having a regular supply of protein is important for building muscle; you should aim for around 30 grams of protein with each meal, should muscle gain be your aim.
You should avoid fatty animal products and beans as they can contain nutrients which cause issues.
The next thing is very important to avoid and a mistake that is commonly made - avoid simple carbs before training. There is so much misguided information regarding the need for simple carbs (sugar) before training, for energy. All that this will do is block your ability to burn fat, as insulin runs riot in your body, storing body fat and not burning it.
I would avoid all types of carbs before training. You will have sufficient glycogen (sugar stored for energy in your muscles) to maintain a high performance during your training.
If you want to eat some carbs, the best time to do this is directly after training. Your body will be more likely to store the sugar they get broken down into as glycogen to replace what has just been used during training within your muscles.
Saying that, you wouldn't want to go and eat half a loaf of bread. The type of carbs you consume is still important. Aim for complex carbs, such as sweet potato, long grain rice and quinoa. These complex carbs take longer to digest and have a lowered insulin response, resulting in less likelihood of fat storage. Aim for around 50 grams after training only and ideally within 90 minutes of exercise.
Lastly, eat natural fatty foods. they are friend not foe. Try to get these from lean meats and nuts.
Nuts are preferable because they don't contain other things which make digestion a more challenging process.
Avoid fats such as those found in bacon, fatty fish and other fatty meats.