Everyone knows at least one — you know, the girl who can eat just about anything and not move a muscle besides the necessary energy it takes to walk from point A to point B… then still not gain one pound. While you might be the girl who works her butt off (literally) to remain at a healthy body weight. Judging by both of your weight, it might seem that each of you are as healthy as the other, but a new study shows that health cannot be judged on weight alone.

According to research reported in Circulation: Journal of the American Heart Association, when it comes to lowering our risk of heart disease and risk of death, fitness level is more important than body weight. Previous to this study, BMI (Body Mass Index) which is a measurement based on weight and height, was the most obvious way to gauge someone’s health. However, this research presents a new test : MET.

MET (Metabolic Equivalent of Task) was used in a study of 14,345 people to see whether BMI or MET was more beneficial in terms of risk of disease and death. The results show with every unit of increased fitness (or MET) over six years was directly associated with a 19 percent lower risk of heart disease and stroke-related death and a 15 percent lower risk of death from any cause. In turn, becoming less fit was linked to a higher death risk all around, no matter what the person’s BMI was.

It might seem confusing as to why a higher BMI might not necessarily mean you are unhealthy. After all, carrying around excess fat is not good for anyone, but this is where the BMI measurement is inaccurate in some cases. By gaining a higher fitness level, you also gain more muscle, which will most likely cause you to add on a few extra pounds of muscle – not fat.

Unfortunately, the BMI measurement does not pick up on what your weight accounts for, so a higher BMI can be misconstrued for a person who has a lot of muscle.

The outcome of this study is good news if you are one of those girls who are physically fit but just can’t seem to lose those few extra pounds. This is proof there is no need to worry about how this effects your health. You are better off working on your fitness than losing weight in the long-run. As long as you keep up your fitness level, your health will stay intact.

Do not feel like you have free range on everything else that effects your body as long as you keep up a consistent fitness routine. Over-indulging on unhealthy foods will have a negative consequence on your body whether you work out a lot or not, so continue to be aware of what you are putting in your mouth. Food is fuel for when you do exercise, and not fulfilling your body’s nutrition needs will result in an unproductive workout. In order to maintain a healthy physical activity level, you must also keep up your energy.

Next time you wake up an hour early just to get to the gym before class or work and you know that other girl is still sound asleep in her bed, just remember what your MET means for your health. Being sluggish, inactive, and unproductive, no matter what your weight, will come back to bite her lazy butt in the end while you will enjoy a long, healthy life full of fitness and happiness.