This was an interesting question raised on a message board. Many posters had varying of opinions; what they felt was the "right" way to lose weight. Although they were completely right about challenging yourself, they used fitness and weight loss as interchangeable terms of goals.
Weight loss is lowering the body weight of one person. It is a tough and complicated concept because genetics and other factors make it hard for a person to lose the weight THEY want to lose it. You must certainly watch how you are eating. Too much, too little, and not the right foods will have effect on your body weight. Of course you should exercise to help your metabolism. As with anything plateaus happen in diet like in exercise, so a good combo of eating for your resting metabolic needs and activity level will help you maintain a "healthy" weight. There are some theories as to why it is harder to lose weight for some people then others, but they are only starting theories nutritionist and other ares of fitness science have begun to look into. It is not that you can't be healthy, but you just might not be the same size as your sister (mine wears a 0 while i am a 10-12). You shouldn't kill yourself just to be a skinny person, you should look at health and keep workouts just out of the comfort zone, something you enjoy, and watch your eating. There has been an influx in licensed professional in nutrition and diet that can help people exactly pinpoint what they need based on their needs.
Increasing fitness defines an umbrella of goals referring to strength, power and speed, and functional activity. You have to always increase stresses to keep the body from adapting to one way of exercising to improve on such goals. While this commonly a goal for the athletes, your average Joe should have something of this in sight because it is a rewarding goal to reach, going from a 3lb weight to a 30lb weight and kettlebells has been a rewarding goal in terms of strength for me. Also with fitness you can improve your heart rate and ward off other medical maladies we face when we do not keep active, although you don't need to go balls to the wall to improve health. Even just walking everyday or keeping an active job or participate in an active sport for fun (Frisbee can be fun and active) can improve health. But the point of always keeping challenged will improve on those goals, but it is not necessary to kill yourself to lose weight, but you can't just take an easy weight out either.
While many run for the high intensity workouts to lose those last few pounds, they might be over doing it for nothing. You should step out of your comfort zone, but not every body will respond the same way. So it is hard to suggest that you should pound it out in the gym in order to be a healthful weight. As with most anything, diet is 80% of that equation. If you don't like high intensity jumping, running, etc then don't do it. Find a decent cardio dance video, step class, or challenging walking program (don't forget your strength with variety of methods because it helps with metabolism) paired with diet can bring people to a healthy weight. On the other hand, if you like that high intensity stuff, then go for it! Just know that your hard work does require a nutritional plan that will feed the body the nutrients it needs to repair itself from such high intensity activities.
You have to always work mentally hard to reach your goals, but you don't have to do Insanity just to lose weight. And don't confuse increasing your fitness with fitting into your skinny jeans. Although you can reach both goals with intensity, don't beat yourself or think you are on the wrong path. Being consistent with your activity and keeping a healthy food plan will certainly help you, you just have to be patient; it didn't come on overnight, you won't lose it overnight. Take the claims in the marketing world with a grain of salt and don't rush for a certain workout because you think it is the magic pill. Keep realistic and you will go to where you need to be.
