Most of us overestimate the number of calories we burn during a workout. We are not Michael Phelps burning 6,000 calories a day or more. This can be one reason you are not having success reaching your goals.
Don’t rely on what the treadmill says. Cardio equipment usually just asks for your age and weight. It doesn’t consider your height, your gender or your body mass (whether you’ve got a lot of lean mass or fat mass). Therefore the calories burned at the end of your treadmill or elliptical or whatever workout is not accurate. You may have burned more but you may have burned less. Your best bet is to wear a heart rate monitor watch that also tracks calories.
You can burn more in shorter time. But… Running intervals for 30 minutes will get you about the same calorie burn as running at a steady pace for an hour. Workout smarter and use the time you have to the max. Keep in mind that you have to do what is best for you. If you are not able to run, then you can perform intervals by walking up and down hills. But remember, you must work hard in those shorter workouts to get the max calorie burn.
Yes, you continue to burn after strength training. But… Strength training is imperative to weight loss. Muscle burns fat and the more muscle or lean mass you have, the more fat and calories you will burn when you are at rest. If you spend an hour strength training and 1/2 of that time is resting and chatting with other gym goers, your burn will not be as high. Also, to build muscle (not bulk, don’t freak) you must challenge yourself. Don’t always choose what is comfortable. At least once per week grab a set of weights that are a little heavier than you are used to and do less reps. (just be safe and smart please and never go beyond keeping proper form). If you have no weights perform isometric exercises like the plank or wall squat where you are holding the exercise for as long as you can to challenge the muscles.