Yes. Obesity is genetic but there are many other non-genetic causes also. If someone has one parent who is overweight they have a decent chance of being overweight themself, if they have 2 parents who are overweight the odds go up to over 80%.
Obesity is better termed "Obesities" meaning there are multiple causes for someone to be overweight and finding your best solution toward a healthier weight is the goal. What works for a friend, co-worker or even physician to lessen their weight may or may not work for you.