Yes, I care. I was like many of the teens here; skinny and could eat just about anything without gaining weight. As someone else mentioned, your metabolism changes sometimes in your 20's - regardless if you are active or not. I didn't care at that point, which meant I put on quite a lot of weight over time. My BMI passed 25, and I noticed the physical changes too late to catch up. After a year or so, I managed to lose most of the surplus weight. At 20, that wasn't a huge challenge, seeing as I had plenty of time to be physically active. A few years ago, I noticed that my weight was increasing again - this time caused by health reasons, which in turn the weight gain made worse. This time I chenged my eating habits (finishing the plate is not a must, only serve portions at the table and always wait 10 minutes before going for a second serving) and started working out regularly. My BMI went from 26 to a healthy 19-20 in about a year, and I have maintained it since. Why should you care about your weight? Most importantly for health reasons. You're not immortal, and your bad habits from when you are young can come back and haunt you later, when you have a lot more to risk, such as children/family, work, economy and property. Appearance. How other people perceive you is a lot based on first impression. Overweight =/= lazy, but unless you show that you have a lot of energy, it can definitely count against you in a job interview where you compete with a selection of top tuned applicants. Since overweight increases the risk of several diseases, many people in the position of hiring choose to avoid those with weight issues to decrease the risk of work days lost. In addition to this, you are less likely to get chosen for jobs where you need to look presentable, and the number of jobs where this is important is increasing. Self worth. If you don't care about your weight and the consequences, you aren't the best you that you can be. Apathy in any form will at some point make you feel bad, and everyone should feel that they deserve to be as healthy as possible, have a nice environment where you live (whether it being an apartment, a dorm room or a house), a job/study and people in your life that treat you well. If you settle on these things, you are likely to regret it later. Life is too short for regrets. :)