The trick here is not only to avoid all obvious sources of carbohydrate (sweets, bread, spaghetti, rice, potatoes), but also to be careful with your protein intake. If you eat large amounts of meat, eggs and the like, the excess protein will be converted into glucose in your body. Large amounts of protein can also raise your insulin levels somewhat. This compromises optimal ketosis.
Popcorn is a whole grain, so it’s not unreasonable to include it on your green-light food list. However, even “natural” and “light” microwave popcorn is loaded with artificial ingredients, plus sodium and butter—and a ton of calories. This doesn’t mean you have to give up all popcorn though, as air-popped popcorn is a much better alternative. It only contains 30 calories per cup and you can customize it to your liking.
Do not try to lose weight too rapidly. Crash diets and diet pills that promise weight loss are usually bad for you and actually don't help keep the weight off in the long run. Resist the urge to take the "easy" way out and instead stick with a healthier lifestyle. This way you lose the weight and improve your health, helping you keep the weight off in a way that won't harm you in the long run.
"Only doing abdominal-focused workouts, like crunches, won’t help you banish the bulge. Belly fat is simply where your body stores energy, so you need to take a whole-body approach to tackle it. HIIT training (high intensity interval training) is a great way to burn fat and get your heart rate up. Squats, burpees and treadmill sprints are all examples to try."