I read that people living in the desert are usually lean but tend to gain weight when living in cities. So, can I have elves with this trait? Also, are the other traits I’ve listed below suitable for desert-dwelling humanoids?

I read online that desert dwellers are often thin but struggle with weight issues if they switch to a sedentary lifestyle. So, could my desert elves be leaner than the average human if they are healthy, yet overweight if they have a poor diet?

The other traits: large, long ears; very smooth skin with high collagen content; rapid DNA and cell repair; silver, white, or blonde hair to reflect light; slanted eyes with a third eyelid; and sharp eyesight, highly efficient kidneys, tongue that can extract water from food. Are these good traits?