Being Obese Or Thin Linked To Mood Chemical Not Just Eating Habits

Wrong.

"Researchers in the US investigating the effect of the nerve messenger and mood regulator serotonin on the energy metabolism of worms, found that being obese or thin may not just be a result of one's eating habits."

There is not a single entity on the planet that will not gain weight when it consumes more Calories than it burns. (absent rare circumstances which almost no human has)

There is not a single entity on the planet that will not lose weight when it consumes fewer Calories than it burns. (absent rare circumstances which almost no human has)

There is another set of worms here - the researchers.