system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What is it in peoples genetic makeup that makes things like weight problems hereditary?
gpt
For the vast, vast, vast majority: nothing.

Weight problems weren't "hereditary" until the last 50 years or so, and amazingly, they still aren't "hereditary" in the third world. Truly shocking.

Human metabolisms don't vary by more than a few percentage points (accounting for obvious things like sex/height/etc).

Everyone has that one friend who supposedly eats a ton but never gains weight, and they have that one friend who eats "omg so healthy" but looks like a blimp. These are not exceptions. People are just really, really bad at estimating how much they themselves eat, and even worse at estimating how much others eat.

Thyroid issues don't make people obese, either. They usually only account for a ~5% difference if untreated and a 0~1% difference if treated.

The only reason fat parents tend to have fat kids is because they instill bad eating habits and don't teach the concept of delayed gratification to their children.