We hear from others all the time how certain people are “naturally strong”, “big boned” or “genetically predisposed” to being a either good or bad at a certain thing. I am not denying that to be the case, just take a look at this recent post from Precision Nutrition for some glaring facts about individual genetics and metabolism.
My point is that Ability is one thing. Skill is another.
Ability is something you have. Your ability to do something is dependent on a 1 thing - A functioning system. Be it, mental or physical, if it is humanly possible, you should assume that you can do it.
Skill is a learned competency of performing a task. Some people master 1 skill, and other people master another.
As a species, we are all blessed with the same foundational genes. I am not discounting the predispositions found of certain ethnicities, genders or sub-groups etc. I am instead pointing out that the bricks and mortar you are made of is the same stuff your neighbor is made of. Simple as that. Unique genetic dispositions aside then we are all given the same tools for the job 99% of the time. This, is ability.
Skill on the other hand is how you use those ability tools. For example: If you want to lose body fat, you may have to develop the skill to be a little stricter with certain macronutrients than your neighbor. I want to continue to highlight though that your system works the same way. You consume calories via food, processed in the stomach and utilized by the muscles of your body. Consume too many calories and you will gain body fat. Your neighbor may not gain body fat as easily as you. Metabolism and physical activity play a part. But the equation of calories consumed vs calories expended is the same for every given man, woman, child, household pet, and mythical creature.
I beg you then to stop worrying about your neighbors genetic predisposition or ability to have a "faster metabolism" than you. You have the same ability. It is who you are. Noting that your neighbor has a "better/faster metabolism" than you is like claiming they have better fingers than you. You have 10 of them, so do they! It’s a moot point and something that has no bearing on how you do your things.
Long story short. You have the tools you have. Develop those tools and do the best thing you can with them. You are just as lucky as everyone else with 10 fingers and 10 toes. Now let's go eat some meat and vegetables, pick some things up and run for the bus. All things we can skillfully effect no matter our abilities.