Of course it is, for exactly the reasons you state, some people just don't want to "think" about anything.
My mother and her sister were very similar as your daughters. Other than when pregnant my mother never weighed more than 125 in her life, and was close to 5'11". Her older sister, OTOH, always had to struggle with her weight even though she was always the more athletic of the 2. My aunt was never fat, but never looked like my mother either, she's just a big woman.
She will be 75 this month and we enjoy sharing recipes for all sorts of things, including jellies and cookies, and send each other our latest concoctions........my mother passed away a year or so ago.
The only people who are experts on how easy or simple it is to lose weight, are the skinnies, those who never had to fight it. I should know; I used to be one and I had the same snotty attitude.
I had a high metabolism and could eat any thing and any amount of any thing I wanted, and it never showed. I had kids and those days were over. I eat better now than ever and exercise and still fight to not gain weight and lose it if I do.