While I am definitely not a dietician or nutritionist, I have learned a lot of general guidelines that work to reach or maintain a healthy weight. A healthy, balanced diet is a huge part of the battle. You can't out-exercise a poor diet.
1. Eliminate all unnatural sugarsA limited amount of real fruit is fine, but try to eat it earlier in the day (I usually have one piece of fruit with breakfast and possibly a second piece with my second meal... and that's all for the day unless I have a good workout later on). Watch labels for anything with "ose" at the end, as well as corn syrup and many other variations. Almost anything in a package these days has some form of sugar in it. Juice is also off-limits since a very small amount has more sugar than a piece of fruit, and none of the fibre.
2. Eliminate processed foods and read labels carefullyAnything in a package from my experience typically has 20+ ingredients, many of which I'm not entirely sure what they are. If you do buy packaged goods, make sure to read the labels. A shorter list of ingredients that you actually recognize is usually a good sign.
3. Eat lean protein with every mealWorst case scenario, I usually just throw a scoop of protein powder in a shaker cup with some water. Whey protein isolate is also great to put in a post-workout smoothie with some fruit to build and repair those tired muscles. Other great lean proteins are chicken, turkey, fish, shellfish, lean beef, bison, egg whites, non-fat yogurt or greek yogurt, etc.
4. Eat every 2-3 hoursOnce your body gets used to this style of eating, it won't hold onto that weight so stubbornly because it knows when the next meal is coming. This is why starvation diets don't work. Because eventually you'll have to eat, and when you do, your body will cling to those calories because who knows when you're going to feed it again! I also find that when I go more than 3 hours between meals I'm a lot more willing to throw the diet plan away and just eat massive quantities of whatever I want. Eating smaller meals on a regular schedule throughout the day keeps you from ever developing that dangerous ravenous appetite.
5. Eat the right starchy carbsYams, oats, brown rice, quinoa, squash, chickpeas, beans, etc. are all fantastic starchy carbs. You'll need slightly more starchy carbs any day that you're lifting heavy weights for extra energy. I usually eat a serving of starchy carbs at the first 5 (out of 6 meals of the day) on training days and the first 4 on cardio or non-training days.
6. Eat only healthy fatsFats tend to get a bad reputation, but the right fats can actually help your weight-loss progress. Avocados, unsalted nuts, omega 3's and flax are all examples of great healthy fats. Morning and evening are the best times of the day to eat them.
7. Drink plenty of waterMany people are regularly dehydrated, and regularly mistake thirst for hunger.
8. Give yourself a cheat day or cheat meal each weekThis sounds counter-productive, but it really helps! If you're craving something you shouldn't have just remember that once you get to your cheat day you can have it. This helps you stick with the plan mentally, and also keeps your body guessing.
9. Keep a food journalIt really helps to write down everything you eat and at what time. It helps you monitor trends and see where there's room for improvement, even if you don't ever show it to anyone else.
10. Stock your fridge with real food and plan your meals ahead of timeIf you find yourself hungry and don't have anything healthy readily available, what do you think you're going to reach for? Pretty much anything. You'll need lots of fresh veggies, fruit, lean proteins, starchy carbs, and healthy fats all ready to eat when you need to eat them.
Thanks for reading and good luck!