The 21st century is the century of excuses.
People don't like being held accountable for their actions and like to blame their problems on anyone but themselves. This is especially true when it comes to their weight and genetics. When you can blame genetics, you're no longer held accountable for your weight problems and you basically accept defeat.
Nature vs. Nurture
Let's say you have two different people (person A&B) from two different gene pools. Now let's assume that both people follow an identical unhealthy diet and poor exercise regime. Both people visit their family doc for an annual check up and get a fasting blood glucose test, which yield completely different results.
Person A has perfectly normal fasting blood glucose while person B has a sky-high reading and consequently is diagnosed with diabetes. So, if two people followed the same diet and exercise routine, and one person got sick while the other stayed healthy, the difference must be their genetics right? Wrong. Dead wrong.
Person B could have eaten green veggies, ditched the junk food and exercised in order to prevent diabetes. Even though person B wasn't as lucky genetically as person A, they could have controlled their environment and remained disease free. Despite their poor genetics, they still had control.
Genetics vs. Epigenetics
Some people are predisposed to certain conditions, like obesity. When you're predisposed to obesity, unless you do everything you can to control your environment you'll likely end up overweight. That means you can still decide your own fate. It means if you control everything in your environment no one will ever believe you have bad genetics.
Epigenetics is the study of heritable changes in gene expression or cellular phenotype, caused by mechanisms other than changes in the underlying DNA sequence (1). It means that not all genes that you inherited from mom and dad (your genotype) are expressed (your phenotype). Yes, you read that correctly, not all of your genes (good or bad) will be expressed if you take control of your environment.
What if I do everything to control my environment and I'm still not thin?
Only worry about what you can control. I will never be Michael Jordan, Mohammad Ali or Wayne Gretzky. I guess I should never play basketball, learn how to box or play ice hockey. How ridiculous does that sound?
When most people workout they expect to look like Sylvester Stallone in a month. I'll tell you now: you probably need to be born with a genetic mutation to look like Stallone did in Rocky 4 (or a little chemical help). It's unreasonable to believe that everyone can diet down to single digit body fat. It's not unreasonable however to believe that we can all achieve a healthy body weight, a healthy body image and a healthy mind. The point I'm trying to make is that you should never compare yourselves to others and you should only strive to look, feel and perform the best that you can. That's all you can do, worrying about anything else is counterproductive and a waste of your time.
Acceptance & Responsibility
Accept your genetics and who you are but do not accept an unhealthy lifestyle. It's your responsibility to eat your veggies, exercise, get to bed early and decrease stress as much as possible. You can't control everything, but you may be able to control more than what you believe.