No, it isn't.
I have two close friends who are overweight through no fault of their own, who cannot lose significant weight no matter what they do.
And they have been to doctors, dieticians, tried everything and anything short of surgery for more than ten years now and it is very much a genetic problem they cannot shake.
Well, I think one of the problems is that doctors are usually a bunch of morons when it comes to weight loss.
Really it's a matter of physics and biology.
The formula to lose weight is: Burn more calories than you eat per day.
It is almost impossible to not lose weight by following that. It's simple physics and biology (and math).
Are your friends men or women?
Actually this is a consistent problem, your average doctor isn't very good with obesity issues, specialists, nutritionists, trainers are often much more useful.
There's a reason there are a lot more obese people today than 10, 20, 30, 50 years ago, and its not becuase our genetics have suddenly gone haywire, its behavior, specifically usually behavior in an atmosphere of abundance.
Rama, I remember my family doctor giving me a physical, at at the time I was maybe around 20% bodyfat, I can't remember actual percentage. I may have had a bit of a belly, but hardly anything. I was 205lbs.
He put me on the scale and freaked out that I was severely overweight. I remember asking why he thought that, and he said that my BMI was way beyond what I should be. So I asked him what my ideal weight was, and he said it should be 155lbs lol.
I literally started laughing at him. The most lean I have ever been was 173lbs, and I was fucking ripped, 7% bodyfat, and I would get stares like crazy. I wasn't even huge, my arms were like 17" at the time, but I couldn't shake the girls off lol.
The problem is for my type it was extremely hard to keep that level of bodyfat. I'm 18% right now, and I'll be happy if I can get down to 12%.
Most obese people would be overjoyed if they could get to 25%, which is totally doable for 99% of them IMO.